Crude oil flow meters, particularly those used for custody transfer, must be calibrated to satisfy the buyer, seller, and applicable government regulations. This is done by comparing the flow measured by the meter to a “known” value. Allocation and other meters should be “proven” periodically to assure that they are still reading flow rates and volumes within acceptable accuracy.
Crude Oil Fiscal Metering System
Fluid flow metering systems provide vital information for Production planning, product quality control and, for control of the process operations.
Quantity meters of various types, used to provide information, needed for, Supply, and demand logistics. Rate of flow meters, typified by the orifice types, are the most widely used meters for process control and general purposes. Mass flow measurement systems are used for contractual purposes when sales gas strews are transferred directly to customers by pipeline. In these systems orifice meters measure the volumetric rates of flow, other instruments monitor the gas density, pressure and temperature and micro-computers convert these inputs to mass flow units.
Quantity metering is also used when liquid products are transferred by pipeline to shipping terminals or to Customers. Turbine meters measure the rates of flow and integrate then over the export operation time span.
The normal units of measurement employed in quantity, rate of flow and mass flow metering are:
cubic metres (m3) cubic feet (ft3)
Cubic metres/hour (m3/h) barrels/day (bbl/d)
kilograms/second (kg/s) tonnes/day (t/d or tonne/d)
Actual production rate of flow varies from day to day and must be integrated or summated to ensure that the accumulating quantity supplied to the customer will meet contractual requirements by the end of the contract period.
Sometimes flow meters are used for the control of two other main process variables, pressure and temperature. High accuracy of flow measurement is generally not as important as keeping the process variables at the specified values. ‘
Flow meters are essential aids for computing material balances, maximising yields of profitable products, reducing slop production and losses to flares along with economise in fuel consumption.
This is perhaps the most important reason for accurate flow measurement as it relates directly to the company’s income and is a mandatory requirement for determination of royalties and/or taxes payable.
Orifice plates and venturi meters are not normally proven. Primary elements are inspected periodically to assure that the dimensions of tubes, surfaces, plate sharpness, flatness and other dimensions have not changed due to corrosion, erosion, solids build up, pressure surges, hydrate or ice damage. Secondary elements (chart recorders, pressure transmitters, etc.) are checked and re-calibrated to known standards.
Meters can be proven using a master meter, bi-directional prover loop (ball prover) or calibration tank.
Master Meter Prover, to prove with a master meter, the piping is arranged so that a calibrated meter can be installed in series with the meter to be calibrated. The “Master Meter” is calibrated with a sphere prover or by other means at a more convenient location. This method requires an additional meter and considerable transportation and installation effort, but avoids the installation of a dedicated prover for each group of meters.
Ball Prover, a bi-directional ball prover is a U-shaped pipe with a calibrated volume between two limit switches. Flow is directed through the meter into the prover. The flow pushes a ball back and forth through the prover, between the limit switches as con-trolled by a 4-way valve. The volume measured by the meter is compared to the volume of the prover. The design of the ball prover and its connection to the system is beyond the scope of this design guideline.
provers are extremely accurate, but they are costly items, and are normally installed only at points of custody transfer of large volumes of crude oil. Field production equipment is routinely equipped with prover connections. A portable prover is brought to the location on a periodic basis to prove the meter.
Calibration Tanks, another method of proving a meter is to flow the crude oil into a storage tank that can be accurately gauged. Then the flow rate indicated by the meter over a period of time can be com-pared to the volume accumulated in the storage tank. This method is less accurate than a ball prover but may be used as a meter check in the same way.
Mass Flow.
Nest flow meters used in oil and gas production systems employ the inferential method of measurement in which some related property is measured and then converted into rate of flow units. The classical example of this method is the differential pressure meter. When a fluid was passed through a tapered nozzle, or throat, its velocity increased and the pressure decreased in the narrowest part. The flow rate was found to be proportional to the square root of the pressure drop. Modern -meters, such as the orifice plate, the venturi tube, the flow nozzle and the dall tube, all use this principle.
The discrete quantity Volumetric flow meter plays a positive displacement metering device or a positive displacement motor driven pump of variable capacity. The operating principle is equivalent to the cyclic filling and emptying of a container and then counting the cycles completed over a time period.
Mass flow metering systems normally include inferential flow meters and usually contain several of the following instruments:
- Pressure and temperature transmitters,
Densitmeter to measure specific mass,
Rate of flow meter (inferential), and
- Computing device. .
The flow meter measures a volumetric rate of flow, the computer corrects the volume for pressure and temperature variations and finally calculates the mass flow using the formula:-
Mass Flow = Specific Mass x Volumetric Flow
= kg/m3 x m3/s
= kg/s.
GEOFLO Computers
The GEOFLO Meter Run Computer is designed to perform pressure, temperature and density compensation for liquid hydrocarbon products. Numerous instruments are replaced by the computer thus reducing interconnect wiring. The computer display prompts the user thus deleting the requirement for extensive look up tables. The GEOFLO Meter Run Computer performs all calculations as recommended by API, is less expensive than the discreet instruments it replaces.
In addition, capabilities for remote data-acquisition are included, allowing, the instrument to be interfaced into more sophisticated systems.
This instrument is capable of performing all compensation and totalisation functions normally required for a single meter run without the necessity of additional peripheral support equipment.
Smith Systems has used its extensive systems design experience to develop an instrument that is much more than a ordinary microprocessor based totaliser. GEOFLO it a powerful measurement sub-system, designed from the ground up to interface economically to both supervisory computer systems and conventional instrumentation.
GEOFLO Hardware Inputs/Outputs
Temperature Input
The instrument devotes one plug in module in the meter run board for the different types of temperature inputs that required, the temperature input is available for operator viewing. The temperature input is required and used for net flow calculation.
Pressure Input
The pressure input is also available in a standard plug-in module with options of either a 4-20 Ma, 1-5 volts or frequency input module.
Density Input
The density input has a space devoted to receiving either 4-20 Ma or 1-5 volts, or frequency input module.
Discreet Outputs
One output is provided for connection to an external annunciator. This output is present when an alarm occurs that has been configured to activate external annunciator. A second output is provided to activate the meter pulse select logic on the field termination board. This output is present upon command to prove the meter run and a third output provides a 100 millisecond signal upon completion of the last pulse output on a batch and can also be used to drive an annunciator point.
Analog Out put
A flow control output can be provided to interface with a flow control valve on the meter run, using 4-20 Ma output module. An operator configurable reset/proportion algorithm will be used to adjust the flow rate control loop.
Host Interface
One of the two communication ports has been dedicated for interfacing the standard instrument to a supervisory computer. This interface allows the supervisory computer to send commands and to request parameter information. In this manner, one host computer can control several of the meters run instruments.
Printer Interface
The other communications port has been dedicated for a printer interface. The instrument provides a serial interface for connection to a hard copy printer. The printer interface is capable of logging alarms as they occur and printing system parameters and constants.
Non Volatile Storage
All totals, configuration constants, and parameters are stored in non volatile battery backup CMOS RAM. These values stored in CMOS RAM will remain in memory for ten years.
GEOFLO Computer Operation
The GEOFLO Meter Run Computer is designed with three modes of operation in mind: Pipe line operation, Batch loading operation, and Product batching operation.
Although these three modes of operation can be quite different, all have been included in one instrument, through the use and manipulation of the batch records and product records.
The GEOFLO Meter Run Computer contains 3 batch records; current, last, and last last. Batch record information can be viewed on the batch display or batch report. The instrument contains 3 batch setup records; current, next, and next next setup records.
Pipeline operation is generally considered to be a continuous flow of the same product with little or no control involved. A usual pipe line operation does not have a flow control valve as a part of a meter run. Since the flow is not stopped as in a batch, usually a daily report is printed. To use a GEOFLO in this mode of operation, the operator should select to have the daily report printed. This selection is made on the report setup menu. The desired daily report time should also be entered on this menu. This menu also allows the operator to select whether he desires to have his totals reset (new batch record started) upon printing of the daily report.
When all batch records are entered then the batch can be started on Menu 1.2, and the pumps brought on line. From this point normal operation consists of monitoring the batch and meter displays, reports and an occasional modification to the default density in the product record or meter factor in the meter curve report.
Batch Loading, is different from pipeline operation in that a specific amount of product is usually being metered. Instead of a daily report an end of batch ticket is printed. In batch loading the instrument frequently has control of a flow control valve. This allows the instrument to ramp-up to the loading flow rate and maintain that flow rate until a ramp-down point is met.
Meter Factor Linearisation, allows the Geoflo to determine exactly what meter factor it should use at any flow rate from a meter curve entered into the unit. The meter curve is a six point, five segment curve. For each of the six points, a meter factor and corresponding flow rate is entered. This entry sequence plots the meter curve. After a prove sequence, a new meter factor would be entered along with its flow rate into the curve replacing the meter factor and flow rate nearest to the new flow rate in the meter curve. This action would shift the meter curve at the point of the new prove, If a linear curve shift is desired, any new prove should be done at a flow rate already in the curve. The difference between the new meter factor and the old meter factor should be found. This difference should then be added to all meter factor in the meter curve.
During normal operation, the Geoflo, every ten seconds, checks the current flowrate. It then goes to the meter curve. If the flowrate is less than the first entry in the curve, the first meter factor will be used. If the flowrate is greater than the last entry in the curve, the last meter factor will be used. If the flowrate is between the first and last flowrates, Geoflo then finds the two flowrate points which it falls between. Using these two flowrate points and their corresponding meter factors, Geoflo calculates what the meter factor would be at this flowrate using a linear interpolation equation: Geoflo will then use this meter factor to calculate gross volume until the next calculation cycle.
Through the use of the meter curve and the meter factor linearisaton algorithm, Geoflo determines exactly which meter factor should be used for any given flowrate.
Vapor Pressure Curve, is a six point, five segment curve. For each of the six points, a vapor pressure and corresponding temperature is entered. This entry sequence plots the vapor pressure curve.
The data from the vapor pressure curve is used only if the product Being metered is a special API product group 6. The data is used for two purposes.
Every ten seconds, the Geoflo unit checks the average temperature of the current batch. It then goes to the vapor pressure curve to determine which pressure to use as the equilibrium pressure in the CPL compensation equation. If the temperature is less than the first entry on the curve, then the first vapor pressure entry will
be used. If the temperature is greater than the last entry on the curve, then the last vapor pressure entry will be used. If the temperature is between the first and the last temperature curve entries, then Geoflo finds the two temperature points on either side. Using these two temperatures and their corresponding vapor pressures, Geoflo calculates a new vapor pressure using a linear interpolation equation. Then this calculated vapor pressure is used as the equilibrium pressure.
If the back pressure override algorithm for flow control has been enabled, the vapor pressure curve is used to determine a pressure which is used in conjunction with the operator entered differential pressure value to calculate a control pressure value. The control pressure is the minimum operating pressure allowed before the back pressure override takes control of the FCV. The Geoflo unit will begin to close the FCV in order to maintain the control pressure.
GEOFLO Calibration
All calibration of the instrument is accomplished through the keyboard and display. The calibration of each type of module is explained in a step-by step procedure below. The 1 to 5-volt module and the 4 to 20 milli-amp modules calibrated exactly the same and will be handled together.
RTD Module
The only calibration required for the RTD module is entering the value of the precision resistor which, is internal to the RTD module. The value of the resistor for a 100 OHM probe is l10.0 OHMS This is currently the only probe type supported.
Calibration Procedure
1) Display the RTD Calibration Menu.
2) Select selection “1” reference resistance.
3) Enter 110 0 followed by the enter key.
A/D Modules (current and Voltage)
The calibration of the A/D Module is simple and easy to follow. A piece of external equipment is required, for the current module a current source is required that can output 4 to 20 milli-amps, for the voltage module a voltage source capable of outputting 1 to 5 volt.
Calibration Procedure
- Connect the external equipment to the field terminal board on the inputs of the module being tested, refer field terminal board drawing
2) Select the A/D calibration menu (Menu 3.3.3.4) for the module to be calibrated.
Set: the external equipment to input 20 milli-amps or 5 volts depending on the module type.
On the calibration menu read the “RAW CNTS” counter, the counter should stabilise
after 10 to 20 seconds if the counter does not stabilise the external equipment should
be checked.
After stabilisation select, “ #3” calibration range, enter the reading on the raw pulse
counter followed by the enter key. The value should now be displayed in the
calibration range location
- Set the external equipment to input 4 milli-amps or 1 volt depending on the module
type. Repeat step #4.
After stabilisation select, “4” calibration offset, enter the reading on the RAW pulse
counter followed by the enter key. The value should now be displayed in the
calibration offset location.
8) Remove the external equipment. The A/D module is now calibrated.
D/A Modules
Calibrating the D/A module requires a milliamp meter and the flow control valve or flow recorder to be connected to the GEOFLO meter run computer. The following calibration procedure should be followed.
NOTE: In reverse acting mode 20/4 output. A zero should be entered for the calibration offset and a 50000 should be entered for the calibration range before calibration is begun. If the calibration valve goes above the calibration range or below the calibration offset erratic operation will result.
Connect the milliamp meter in series with flow controller or flow recorder at the field terminal board.
Select the flow control menu (Menu 3.1.3) select entry, “3” algorithm, the prompt “O =CAL, 1=PI, 2=FR, 3=BP” will be displayed. A “O” should be entered followed by the enter key. The message beside “3-Algorithm” should now say “CAL”.
Select the D/A calibration menu-selection “4” on the flow control menu.
On the calibration menu select “5” calibration value enter a mid range number of about 10000 followed by the enter key.
Now monitoring the milliamp meter decrease the value entered in calibration value until the meter reads 4 milliaps. Allow the current reading to stabilize before making a new entry.
Enter into the calibration offset, selection “4”, the value required in calibration value to output 4 milliamps.
At this time the flow controller of flow recorder should be zerored.
Now monitoring the milliamp meter increase the value entered in calibration value until the meter reads 20 millamp. Allow the current readings to stabilize before making a new entry.
Enter into the calibration range, selection “3”, the value required in calibration value to output 20 milliamps.
- At this time the flow controller or flow recorder should be set for maximum reading.
Remove the external equipment, the D/A module is now calibrated.
Frequency Module
The calibration of the Frequency Module is simple and easy to follow. A frequency generator capable of providing a frequency range comparable to the range of the probe is required.
Calibration Procedure
Connect the frequency generator to the field terminal board on the inptus of the module being tested, refer to field terminal board drawings.
Select the Frequency Nodule calibration menu (Menu 1.3.4.6) for the module to be calibrated.
Set the frequency generator to input the maximum frequency for the range of the transducer.
0n the calibration menu read the “RAY CWS” counter, the counter should stabilise after 10 to 20 seconds. If the counter does not stabilise the frequency generator should be checked.
After stabilisation, select “3”, calibration range, enter the reading on the Raw Pulse counter followed by the enter key. The value should now be displayed in the calibration range location.
Set the frequency generator to input the minimum frequency for the range of the transducer. Repeat Step #4.
After stabilisation, select “4” calibration offset, enter the reading on the Raw Pulse counter followed by the enter key. The value should now be displayed in the . calibration offset location.
Remove the frequency generator. The Frequency Nodule is now calibrated.
GEOFLO MAINTENANCE
Maintenance of the GEOFLO instrument is limited to replacement of fuses and printed circuit boards. After it is determined that all input voltage and field wiring are correct, refer to the troubleshooting table, attached document, to determine the most likely cause for the failure.
METER PROVER LOOP
At each station where positive displacement meters (pdm) are used there is an associated prover loop. The purpose of the loop is to check pdm accuracy. To do this it independently measures the oil passing through the pdm by diverting it through a long pipe of accurately known volume. The flowing oil moves a sphere along the pipe and the sphere’s movement is timed by electrical switches triggered by its passage. Simultaneously the metered volume is recorded and a comparison is then made between the known volume displaced by the sphere and the meter reading. If there is a large error then the meter must be serviced, if the error is small it is then incorporated into a correcting meter factor.
In transparency T7 the directional arrows indicate fluid flow paths. This illustration also indicates the major elements. Whenever fluid is passing through the meter, the meter produces a relatively high frequency signal output which is directly proportional to fluid volume through the meter.
Prover Operation
Flow passes through the meter, into the diverter valve, and down through the prover run. The flow pushes the spheroid along to trigger the detector switches, eventually depositing it in the receiving chamber. The flow then continues around the spheroid and out to the line.
When the spheroid passes the first detector switch the meter prover counter is triggered into the registration mode where it remains until it is triggered to the non- registration mode when the spheroid passes the second detector switch. The total number of pulses accumulated on the prover counter while the spheroid is moved between the first and second detector switches is then compared to the predetermined
volume of the prover section to ascertain meter factor.
The prover cycle in the bi-directional type prover is one round trip of the spheroid which is equivalent to the sum of pulses accumulated on the prover counter as the
Spheroid travels in each direction between detector switches. The spheroid direction is changed by changing the flow which in turn. is accomplished by changing the mode of the 4.way diverter valve.
Experience has shown that most proving inaccuracies are caused by one or more of the following:
a improper sizing of the spheroid,
b air trapped in the system while proving,
c poor heat balance, or temperature stabilization,
d improper valve manipulation by the operator,
e electrical connections not properly made up.
If the following suggested procedures are followed, the above possible sources of trouble can be eliminated.
Sizing the Sphere
The sphere is normally inflated with water to a size somewhat larger than internal diameter of the pipe. Sizing is most easily accomplished by the use of a gauging ring.
Once the sphere is sized to make contact with the pipe wall and effects a seal, further
inflation will not improve its sealing efficiency appreciably. Over inflation will not
cause serious harm, other than increasing the wear rate needlessly. Under inflation results in excess bypass and inaccuracies. Even though the sphere may produce repeat runs when under inflated they will probably be in error.
The sphere seldom needs resizing. Since wear is generally a function of lubricity, crude or lubricating oil service gives exceptionally long life.
Resizing of the sphere can generally be done periodically, along with other routine maintenance. Normally several hundred runs can be made without resizing the sphere. However, it is good practice to check the sphere whenever convenient.
Purging Air
If the prover is empty, prior to proving the meter, it is best to fill behind the sphere, allowing the sphere to displace air ahead of the liquid. Vent air through all vent valves. Once the sphere has made its initial trip, run it back and forth several times while bleeding trapped air through the various vent valves.
Heat Balance or Temperature Stabilisation, this is partially accomplished at the same time that air is being purged. Under extreme ambient temperature conditions it is good practice to allow liquid to flow through the prover for several minutes, or until the thermometers indicate that temperatures have stabilised.
Valve Manipulation
The four-way diverter can be shifted quite rapidly; however, to avoid hydraulic shock loads to the system, shifting the unit through 90° in two or more seconds is recommended. Note that the four-way diverter must be shifted prior to the time the sphere strikes the first detector, otherwise some of the metered fluid may bypass through the manifold. This could result in inaccurate data.
A little practice will result in the operator developing a good ‘feel’ for operating the diverter. The diverter must be operated more quickly at higher flow rates.
Electrical Connections
Poor maintenance of connectors, or carelessness, can result in improper electrical connections. Cable connections should be kept clean and free of water, din and other foreign matter. Make sure that connections are tight and positive when connecting electronic components.
It is a wise procedure to make several practice runs prior to recording data for the formal meter proving. This enables the operator to determine that all components are
working properly, it also gives enough preliminary data to indicate that the results will be of the right order.
Recommended Proving Procedure
Preparation;
- Install thermometers and pressure gauges, if not already in place.
Position four-way diverter so that fluid will enter prover behind the sphere.
Open vent valves.
Place prover on stream, purging air ahead of sphere while it makes its first run.
Reverse flow causing sphere to make a return run.
Allow fluid to circulate, or make a few more runs while making electrical connections.
Connect detector cable to counter unit.
If necessary, install tachometer on meter to be proved.
Attach tachometer cable to counter unit.
Energise counter power supply.
Check operation of counter and electronic components as outlined in
manufacturer’s instructions. Reset counter to ‘Zero’.
- Check thermometers to determine if temperature has stabilised.
- Make practice run – round trip – and check preliminary data shown on counter.
Proving operation
Fill in standard data on meter proving report forms.
Set counter to ‘Zero’.
Note average temperature and pressure across loop, and at meter. Record
averages.
Stan proving run by operating four-way diverter.
Do not reset counter at end of first run (allow it to total second run of round trip).
When sphere completes first run, reverse valves to staff sphere back for second half of round trip. ‘
Record average temperature and pressure across loop, and at meter.
Note final counter reading, and reset to ‘Zero’.
Record data for round trip.
GEOPROV Computer
The GEOPROV instrument is an 8088 microprocessor-based electronic proving instrument designed by Smith System. This instrument is capable of the necessary monitor, control, and calculation requirements of the proving operations of a bi-directional prover. GEOPROV is built primarily with CMOS components. This gives the advantages of low power requirements and high immunity, both of which, are features which, other microprocessor-based instruments do not have.
GEOPROV Computer Operation
After entry of the operating parameters, an external meter pulse select, and an external detect switch select, the operator may initiate an auto-prove by selecting “Prove commands” on the main men” display. (Menu # 1) Meter I. D., product density product group and the K Factor of the meter being proved must be entered through the meter data menu (Menu # 1.2.1.2) if there is no communication to a GEOPROV unit. The meter temperature, pressure, and flow rate may be viewed through Menu # 1. 2. 1. and Menu # 1.2. IA prior to a start prove request. The auto prove algorithm will generate a prove sequence for the number of consecutive trips if the prover pulses are repeatable within the pulse deviation limit or the total number of trips if the prover pulses are non-repeatable. An abord prove can be initiated at any time through the “prove Commands” menu (Menu # 1.2).
Manual Valve Control of the 4-May valve is available through the valve control menu (Menu # 1.2.5). A selection of either command (forward or reverse) from the menu will initiate the respective command to the valve. Valve status (forward, reverse, internist, or
error) are shown as part of the valve control menu so monitoring of the valve can be done easily by the operator.
GEOPROV Functional
1) Valve Sequencing:
The 4-May valve is rotated sequentially from one flow direction to the other until a sufficient number or prover runs, within the pulse deviation limit, have been accumulated. Upon a prove request or an abort prove, the 4-May valve is cycled in the reverse direction in order to locate the sphere in the home launch chamber
2) Seal Monitoring:
The 4-May valve seal seat-us -is monitored during the period the
sphere is between detector switches.
3) Continuous Prover operation:
detector switches are monitored after the 4-Way valve is cycled. When the first detector switch is activated, the prover pulse counter starts to accumulate meter pulses. Activation of the second detector switch terminates the accumulation. After a ten second delay, the 4-way valve is rotated, with the sphere travelling in the opposite direction, pulses are again accumulated between detector switches. This sequence is continued until enough round trips are achieved when fall within the pulse deviation limit requested, or the maximum allowable round trips is reached.
4) Parameter Monitoring During a Prove:
After a prove request, there is a 30 second stability delay after which, the prover inlet and out let header temperatures are averaged if inlet header temperature is available and then compared to the meter temperature, otherwise only prover outlet header temperature is compared to meter temperature if the difference exceed the abort parameter, delta temp, this cycle is repeated for the amount of time pre-entered by the operator. After which, the prove is aborted due to Temperature instability. If the temperatures are within the limit, the prover temperature and meter temperatures are both stored for later averaging calculations. The prover inlet and outlet header pressures are averaged (again only if inlet header pressure is available) and stored along with the meter pressure and the first round trip is initiated.
As soon as the second detector switch, is activated, the prover temperature is compared to the meter temperature at the start of the prove. If these temperatures drift outside the delta temp limit, the prove is aborted due to Temperature Instability.
If the allowable pulse deviation limit on a round trip is exceeded, causing previous trips to be discarded, the sequence of temperature measurements and checks described above are repeated.
GEOPROV Calibration
All calibration of the instrument is accomplished through the keyboard and display. The calibration of each type of module is explained in a step-by step procedure below. The 1 to 5-volt module and the 4 to 20 milli-amp modules calibrated exactly the same and will be handled together.
RTD Module
The only calibration required for the RTD module is entering the value of the precision resistor which, is internal to the RTD module. The value of the resistor for a 100 OHM probe is l10.0 OHMS This is currently the only probe type supported.
Calibration Procedure
1) Display the RTD Calibration Menu.
2) Select selection “1” reference resistance.
3) Enter 110 0 followed by the enter key.
A/D Modules (current and Voltage)
The calibration of the A/D Module is simple and easy to follow. A piece of external equipment is required, for the current module a current source is required that can output 4 to 20 milli-amps, for the voltage module a voltage source capable of outputting 1 to 5 volt.
Calibration Procedure
- Connect the external equipment to the field terminal board on the inputs of the
module being tested, refer field terminal board drawing
- Select the A/D calibration menu (Menu 3.3.3.4) for the module to be calibrated.
Set: the external equipment to input 20 milli-amps or 5 volts depending on the
module type.
On the calibration menu read the “RAW CNTS” counter, the counter should stabilise
- after 10 to 20 seconds if the counter does not stabilise the external equipment should
be checked.
After stabilisation select, “ #3” calibration range, enter the reading on the raw pulse
counter followed by the enter key. The value should now be displayed in the
calibration range location
- Set the external equipment to input 4 milli-amps or 1 volt depending on the module
type. Repeat step #4.
After stabilisation select, “4” calibration offset, enter the reading on the RAW pulse
counter followed by the enter key. The value should now be displayed in the
calibration offset location.
Remove the external equipment. The A/D module is now calibrated.
GEOPROV MAINTENANCE
Maintenance of the GEOPROV instrument is limited to replacement of fuses and printed circuit boards. After it is determined that all input voltage and field wiring are correct, refer to the troubleshooting table, attached document, to determine the most likely cause for the failure.
CAUTION: All power must be removed before proceeding with the continuity checks or resistance measurements, or when plugging in or unplugging printed circuit boards and front panel assembly.
Handle printed circuit boards by the edges to prevent static charge damage of electronic circuitry.