High Resolution Transducer Troubleshooting Guide

The System Studies High Resolution Transducers have proven to be relatively trouble-free. However, there are certain conditions that may require your attention. Several of these are listed below. Also listed are possible solutions to each condition or problem. If the problem persists after following the instructions below, please contact the System Studies Technical Support Department.

Troubleshooting
To manually verify flow measurements, both the Flow and Dual High Resolution Transducers are equipped with two tank valve fittings and a locking stud, which are designed to mate with the sampler attached to the twin tubing on the System Studies Flow Gauge. (See Figure 1 below.) The Dual Transducer's high side (banded) tank valve can be used to verify transducer readings with a C pressure gauge. High Resolution Pressure Transducers are equipped with a single pressure testing valve for taking manual measurements with a C pressure gauge.

The System Studies Transducer Test Meter should be used where noted to measure the current output of the transducers. The Transducer Test Meter will display flow (SCFH) and pressure (PSI) readings with an accuracy of 1.2 % of full scale. Instructions for using the Transducer Test Meter are given in the last section of these guidelines.

Error Conditions

• OPNI/0.00-0.02 mA—This reading implies that the pair being read is not connected to a transducer. When transducers fail, they read shorted or default to approximately 3.2 mA. If a transducer gives a reading between 0.00 mA and about 0.02 mA, pair ID or continuity is in question.

• PAIR Continuity—Verify the pair by shorting the leads while performing a Realtime Reading through PressureMAP.
  • If the pair is correct, use a Transducer Test Meter to check the operational status of the transducer.

    Note: The pair leads must be disconnected from the transducer to accurately measure it with the Transducer Test Meter.

  • If the shorted pair does not show up in the Realtime Readings, trace the continuity of the pair, from the 289H relay card amphenol connector to the CO block, and then to the transducer.

• PAIR/3.2 mA—The minimum current that a transducer will draw is 3.2 mA. The PAIR reading may be caused by reverse flow across the Flow Finder orifice (i.e. cable feeding air pipe), a reversed transducer hookup across a Flow Finder orifice (transducer's high and low pneumatic inputs reversed), or a failed transducer.

• Reversed Air Flow Connections
  
  • Use a proven gauge to determine the true direction of air flow at the Flow Finder or manifold monitored by the transducer. Do not assume the hookup of the hoses is correct, verify that it is.

  • If the air flow direction is correct, disconnect the air to the transducer, opening both of the inputs to atmosphere. If possible, allow at least 1/2 hour for the sensor to stabilize before taking a reading. If it is not allowed to stabilize, the transducer may read as much as 0.2 mA lower than the actual value. Read the transducer using PressureMAP Diagnostics' Realtime Reading function.If the reading moved up at all, to approximately 3.5 mA or more, the transducer is OK.

• Grounding Problems
  • If the transducer checked out as OK in the previous step, the grounding in the CO may be faulty, and needs to be checked. The frame ground from the 289H utility card should lead to the CO ground bus as directly as possible. Also, the CO power supply earth ground should be as direct as possible. Problems may occur if long, meandering ground leads are used.

• PAIR/3.6 mA—This reading indicates a transducer with a low zero calibration, assuming there is no flow across it at the time of the reading. The typical acceptable zero calibration window is from 3.750 mA to 4.025 mA. Readings near 3.750 mA, but slightly off, point towards a low zero calibration. This reading may also be caused by a slight backward flow or hookup reversal with a slight forward flow.
  • To determine the true direction of air flow at the Flow Finder or manifold monitored by the transducer, use a Flow Gauge. Do not assume the hookup of the hoses is correct, verify that it is.

  • If the air flow direction is correct, disconnect the air to the transducer, opening both of the inputs to atmosphere. If possible, allow at least 1/2 hour for the sensor to stabilize before taking a reading. If it is not allowed to stabilize, the transducer may read as much as 0.2 mA lower thanthe actual value. Verify the reading using either PressureMAP diagnostics or the Transducer Test Meter. Remember, the pair leads must be disconnected from the transducer if using the Transducer Test Meter. If the reading indicates that the calibration is off, contact System Studies Technical Support for further instructions.

• SHRT—This reading indicates a pegged transducer, a shorted pair, or a failed transducer.
  • Take a manual reading with a Flow Gauge to verify the actual flow. If the reading is twice the rating marked on the Flow Finder or manifold monitored by the transducer, the transducer may be pegged and needs to be upsized.

  • Disconnect the pair from the transducer while monitoring the readings using PressureMAP Diagnostics. If the reading is still a short, the transducer is OK, but the pair may be incorrect or damaged.

  • Disconnect the air source at the transducer, and perform a Realtime Reading through PressureMAP Diagnostics. If it still reads short, disconnect the pair at the transducer and check the transducer with the Transducer Test Meter.

• Erratic/Jumpy Readings—The grounding in the CO may be faulty, and needs to be checked.
  • The frame ground from the 289H utility card should lead to the CO ground bus as directly as possible. Also, the CO power supply earth ground should be as direct as possible. Problems may occur if long, meandering ground leads are used.

Additional Note on Grounding Symptoms
Any symptoms noted above that are related to the 289H grounding may also be caused by pairs bundled together with the CO power supply cabling. Noise from the power supply can couple over to the pairs and influence the readings, causing reading errors or erratic measurements.

Transducer Test Meter Instructions
This section provides detailed information on the proper use of the System Studies Transducer Test Meter (P/N 9800-3600). Similar instructions are supplied with the product (Figure 2).

Prior to connecting test leads to device pairs or terminals, check the condition of the test meter’s internal battery power. Readings taken with a low battery will be inaccurate. It is also important to make sure the meter is zero adjusted before taking readings (see procedures below).

Transducer Test Procedure

Note: Flow and pressure measurements must be made separately.

Procedure:

The following procedures explain how to test System Studies’ 4 to 20mA monitoring devices using the Transducer Test Meter.

1. Connect the meter’s red and black leads to the monitoring pair of the device being measured. It is not important which leads are connected to which conductor—unless you are testing devices on a Selector Pair Saver™ device circuit (see explanation below).

2. Evaluate the reading as indicated on the pressure or flow scale of the meter. For readings in the OPEN, 0, and SHORT scale regions, see “Off-scale Readings.”

For pressure transducer output, use the values listed below the curved scale on the gauge face. Reading increments are 0, 10, 20, and 30 PSI. Transducer output that falls between two indicated PSI values is estimated (Figure 3). Flow readings (numbers on top of scale) are read as a fraction of the flow range listed on the Flow Finder to which the transducer is connected. Flow Finder ranges are 0–95, 0–47.5, 0–19, and 0–9.5 SCFH.

A reading of “FS” (Full Scale), when testing a flow transducer connected across a 47.5 SCFH Flow Finder, indicates a measured flow of 47.5 SCFH; a scale reading of “1/2” indicates a flow of 23.75 SCFH (0.5 X 47.5). System Studies’ monitoring devices are also capable of reading up to twice the rated Flow Finder range. The Transducer Test Meter will indicate extended ranges as either “1.5 X FS ” or “2 X FS.”

Testing Selector Pair Saver Installations
System Studies’ Selector Pair Saver device (P/N 4990) makes it possible to read and monitor two 4 to 20 mA transducers using only one device pair. Procedures for testing both transducers at the Selector Pair Saver are as follows:

Procedure:

1. Connect the meter’s red (positive) lead to the white (tip) conductor of the Selector Pair Saver’s outgoing blue/white pair. Connect the black (negative) lead to the blue (ring) conductor (Figure 4).

2. To test the first transducer (the one connected to the orange/white pair), move the polarity switch (bottom-right switch) to the “Device #1” (DOWN) position. To test the second transducer (green/white pair), move the switch to the “Device #2” (UP) position.

3. Readings are evaluated as described in Step 2 of the Transducer Test Procedure.

Off-Scale Readings
“OPEN” Reading. OPEN readings indicate that insufficient current is flowing in the device loop. Using the previous test procedures as a reference, verify that the connections to both the meter and the device are correct. Also check to see that the battery is functioning properly. If all external connections are good, an OPEN reading means the monitoring device could be faulty.

“0” Reading. A meter reading of 0 indicates a flow of zero, or atmospheric pressure (0 PSIG). A properly functioning device with both pneumatic inputs disconnected (vented to atmosphere) will read in this region.

“SHORT” Reading. A SHORT reading indicates an over (excessive) current condition in the device. If the meter reads SHORT, verify that the test meter or pair leads are not touching each other. If they are not, the device could be faulty.

Other Readings.A meter reading in the uncolored region between OPEN and 0 indicates one of the following conditions.

• If both pneumatic inputs of the device are open to atmosphere, a reading on the left side of this region indicates a possible failed device.

• A reading toward the right of this region could indicate that the transducer has a low zero calibration. Low zero calibration can be verified by placing a pressure transducer under pressure or creating a flow across a flow transducer (at the Flow Finder). If the reading increases, the transducer is functional but must be recalibrated.

• If the device is connected to a Flow Finder in a pressurized system, a reading to the left side of the uncolored region can indicate a reverse flow. Check the Flow Finder pneumatic connections to the transducer for proper orientation. This type of reading could also be caused by cable pressure that is higher than air pipe pressure. Although this is rare, it is possible in an air-tight system. Test the transducer with both pneumatic input ports vented to atmosphere to check for this condition.

Testing the Battery
The Battery Test button and LED indicator on the front cover of the unit are used to verify that the battery charge is sufficient for proper test meter operation. Simply press the button (with power on or off) to check the battery. If the LED illuminates, the battery charge is acceptable. Replace the batteries if it does not light (see replacement procedures below).

Note: The battery test is independent of the operating mode of the meter. It neither affects the readings, nor is it affected by being connected to a transducer.

Zero Adjusting the Meter
To verify that the meter is properly zeroed, turn the power switch on. If necessary, using a flat-blade screwdriver, turn the zero-adjust screw located on the gauge face in either direction until the meter’s needle lines up with the “meter zero” line. Because the meter is slightly position sensitive, it is recommended that you both zero adjust and take readings holding the meter in the same orientation (either vertical or horizontal).

If you have any questions about troubleshooting High Resolution Transducer problems, please call System Studies Technical Support Department at (831) 475-5777 or (800) 247-8255. You can also submit your questions via e-mail.