Transducer/Contactor Troubleshooting Guide

The following information can be used with the PressureMAP 289H LSS Diagnostics feature to identify transducer and/or contactor reading problems. These problems are indicated by fluctuating device readings or by one of PressureMAP's verbose messages (such as: PAIR, UBAL, OPEN, SHRT, or VOLT).

There are three primary causes for these problems:

• Monitoring Pair Trouble
• Bad Transducer (inoperative device, out of calibration, etc.)
• Inaccurate data entry (incorrect TD Type, wrong range, etc.)

This guide describes procedures for troubleshooting problems with current loop pressure and flow transducers, resistive pressure and flow transducers, and contactors. Included at the end of the guide are five tables that convert transducer output to the appropriate resistive or loop current values. These tables can be used with the troubleshooting tips described below.

Before accessing the 289H LSS Diagnostics program and performing the procedures described below, you should do some basic preparation. Read this booklet over first and identify the test(s) you will need to run for your specific problem. You'll also need to have device numbers on hand, and make arrangements, if necessary, to have someone assist you from the field. These preparations will prevent PressureMAP from timing out (dropping the connection to the 289H) while you're working in the 289H LSS Diagnostics program.

Accessing the 289H LSS Diagnostics Menu
The 289H LSS Diagnostics Menu is available from Option 6 of the MAP Programs Menu. This is the second screen in the PressureMAP menu structure.

Beginning at the System Options Menu, you can access the 289H LSS Diagnostics Menu as follows:

Select 1 and Enter

Select 6 and Enter

After selecting CPAMS Diagnostics, PressureMAP prompts you to enter either the office name or number, followed by the key. It then calls the selected 289H LSS office, issues a prompt when the connection has been made, and displays the 289H LSS Diagnostics Menu shown below.

Note: For the troubleshooting procedures described below, only the following menu options will be used:

• Realtime Reading Test (option #3)
• Specific Device Info (option #4)
• Capacitance Test (option #5)
• Leakage Test (option #8)
• AC Test (option #9)
• DC Test (option #10)

Troubleshooting Current Loop Transducers
There are a number of tests that can be performed on System Studies' 4-20 milliampere (mA) pressure or flow transducers that have generated a verbose or fluctuating reading.

Realtime Reading Test: Devices Reading PAIR

Step 1
Select Option 3 from the 289H LSS Diagnostics Menu and enter the device/access number of the transducer with the problem. You'll see a screen like the one below.

This realtime reading displays six columns of data, including Access #, Type, Milli-Amps and Reading. For these troubleshooting procedures, the information in the Milli-Amps and Reading fields is the most important. (However, please note that a Status indicator message is the precursor to the corresponding "verbose" reading.)

Step 2
Let the Realtime Reading display run for about ten cycles or readings. The type of output displayed in the Milli-Amps field (fluctuating or constant) is useful for troubleshooting.

Analysis:

1. A correct reading for a current loop transducer in the Milli-Amps field is between 3.8 and 20.0 mA. If the device is not within this range, it will read PAIR.

2. If the milliampere reading is in the range of .2 to .7 mA, there's a possibility that the device is a resistive transducer that has been input into the PressureMAP database as a current flow device.

3. If the reading in this field is above 20 mA, there's probably a short on the pair (pair trouble). (Check the explanation below on "Leakage" for additional information.)

4. Transducers that read in the range of 3.0 to 3.6 mA (and the value holds fairly steady) indicate an out-of-calibration condition.

Leakage Test: Devices Reading PAIR
Current loop devices that read PAIR and have a value of .2 to .7 mA indicated in the Realtime Reading Test can be further tested to see if they are actually resistive devices. For this situation, you would use the 289H LSS Diagnostics Leakage Test.

Step 3
Pull up the Leakage Test by selecting option 8 from the 289H LSS Diagnostics Menu. You'll see a display similar to the one below.

Notice that this screen has four columns of data with the following headings: Access #, Tip/Ring Ohms, Tip/Gnd Ohms, and Ring/Gnd Ohms.

Analysis:

1. A leakage resistance value between 1,000 and 9,000 ohms (in the Tip/Ring Ohms column) represents a valid reading for a current loop device. On the other hand, a reading of approximately 700 ohms or less would indicate pair trouble ( you've got a short on the pair).

2. If the reading in the Tip/Ring Ohms column of the Leakage Test display is a value between 100K ohms and 3.8M ohms, this indicates that the transducer is a resistive device, not a current loop one.

3. By looking at the values in the Tip/Gnd Ohms and Ring/Gnd Ohms columns, you can determine much about the quality of the pair. For example, a good clean pair would have resistance readings of 10M ohms and higher in both columns. A reading below 10M ohms in either column, for example, would suggest that the pair is not real clean and may be the reason for fluctuating readings.

Note: It is possible to use current loop transducers as Ring to Ground devices, but this method is rare.

AC Test

The next 289H LSS Diagnostics Menu option (#9) is used to check the amount of alternating current (AC) on the pair. A Volt Status indicator is displayed for excess AC voltage (6 VAC or more); a VOLT reading is created by lethal AC voltage (12VAC or more). A message indicating excessive voltage is often found on device pairs that monitor central office air dryers. Another example of where this reading would occur is on a pair located in a specially designated monitoring cable that has not been correctly bonded and grounded.

The screen below contains the type of data provided in the AC Test.

Analysis:

1. Once again, the AC voltage indicated in the VAC Tip/Gnd and VAC Ring/Gnd columns should be 1.0 VAC or less. If you have 5 or 6 volts, you're definitely picking up voltage from another power source.

2. Low AC voltage—a value less than that required to cause a VOLT reading—could show up as a fluctuating reading in the Realtime Reading Test.

DC Test

The next 289H LSS Diagnostics Menu option (#10) is used on both current loop and resistive devices to determine if a pair has excessive direct current (DC) voltage. A truly clean pair should have no voltage; but if excess voltage is detected on the pair (10 VDC or above), PressureMAP will display a Volt Status message in Realtime Readings. Lethal voltage (42 VDC or above) will generate a VOLT reading. When selecting this option, followed by the device number, you will see a screen similar to the one below.

Analysis:

1. Readings in the two VDC columns should be under 1.0 volt as shown above. A reading over 2.0 volts is significant, and when this occurs, you will probably see resistance as well (refer to Leakage Test above). If this is the case, you can either switch to a good pair or shoot the trouble to correct the reading problem.

2. If voltage is 1.0 VDC or less, it may result in a PAIR reading, but it could also show up as trouble or leakage.

Capacitance Test

The value of the 289H LSS Capacitance Test is its ability to confirm an open circuit on a device pair and provide an indication of whether the open is inside the office or out in the field. The PressureMAP reading would indicate either OPNI (designating an open inside the office) or OPNO (outside the office). For troubleshooting either condition, the most valuable information is located in the K-feet and Loc. columns.

Analysis:

1. If the values in the K-feet columns in both the Tip Side and Ring Side sections of the display are in the range of 0.1 to 0.5 kilofeet (100 to 500 feet), for example, this would confirm that the open circuit is inside the office.

   It is important to remember that there is a lot more wire in the office than most people realize. So, if you see 0.3 or 0.4 kilofeet in the K-feet columns, there is probably a jumper missing from the frames to the 289H equipment.

2. A lot of times one side of the pair will be open. For example, you might see 15.5 on the Tip Side and 3.0 on Ring Side. In this case, there's an open on the Ring Side approximately 1/5 of way out on the loop (3,000 feet).

Incorrect Readings

There are a number of things you can check when the Diagnostic Tests described above indicate that everything appears to be O.K. except for the actual reading.

Flow Transducers

1. Check that the correct flow range for the device has been entered into PressureMAP. You can use option #4 (Specific Device Info) from the 289H LSS Diagnostics Menu.

2. Make sure you are on the right pair. You may have to arrange for someone to create a short at the transducer while you run a Realtime Reading Test (option #3). If this doesn't produce a reading change, you'll have to locate the correct pair.

   Note: PressureMAP generates a SHRT reading when the measured current is above 33 mA. (Prior to Version 21, this message was generated by readings above 30 mA.)

   If the device with the incorrect reading is a High Resolution Dual Transducer, it is possible that someone may have wired both sensors incorrectly. Switch the connections on the transducer's barrier plate by first removing the wire cover assembly.

Pressure Transducers

1. Check the pair as explained in item 2 above.

2. Identify the type of High Resolution Pressure Transducer. Some of the earlier transducers were calibrated from 0 to 15 PSI and required a CPA/15 Transducer Type. The more recent devices have a different zero calibration, and they require a CPA/30 Transducer Type in PressureMAP in order to produce a correct reading.

3. If a pressure transducer reading is consistently inaccurate (when compared with a manual reading), check to see if there is a Barometric Pressure Transducer installed in the office. Without the Barometric device installed and input into PressureMAP, readings will be off by approximately 0.5 PSI per 1,000 feet of elevation.

   Note that if the Barometric device is input into PressureMAP, but not wired to the 289H LSS, the readings for all pressure transducers in the office will be 14.7 PSI (or one atmosphere) too high. (This is because the High Resolution Pressure Transducers are calibrated at sea level to read absolute, not gauge, pressure.) So, if this is the case, either wire the Barometric Transducer or disable the device in PressureMAP.

Troubleshooting Resistive Transducers
Many of the tests described above also pertain to resistive pressure and flow transducers. For example, all of the Capacitance, AC and DC Test suggestions previously described can be used for resistive devices. For this reason, they are not repeated in this section. What follows are some tips on how to use the Realtime Reading and Leakage Tests to troubleshoot PAIR, SHRT and UBAL readings on resistive devices.

Realtime Reading Test

If the device is reading PAIR, SHRT or UBAL, initiate a Realtime Reading by selecting option #3 from the 289H LSS Diagnostics Menu and entering the appropriate device number. You will see information similar to what's displayed below. Notice that this information has an Ohms column, which contains the key information for troubleshooting these types of transducers.

Analysis:

1. A resistive transducer that is reading correctly will have an Ohms value between 100K ohms and 3.8M ohms (refer to the pressure and flow transducer conversion charts for resistive transducers located at the back of this guide).

2. If you see 1K ohms to 9K ohms across the pair, chances are it's a current device.

Leakage Test

The leakage test can be used to confirm a PressureMAP PAIR, SHRT or UBAL reading. It will indicate if the device generating the reading is actually a resistive transducer or a current loop device. When you initiate a Leakage Test (option #8 from 289H LSS Diagnostics) for the selected device (access) number, you will see a screen similar to the one below.

Analysis:

1. The data in the screen sample above represents a good pair. Notice that there is between 100K ohms and 3.8M ohms across Tip and Ring (column 2), and above 20M ohms in the both the Tip to Ground and Ring to Ground columns.

2. You will get a UBAL, or unbalanced pair, reading for a resistive device when one or both sides of the pair has excessive leakage to ground (as shown in the screen below). But it could also indicate that an incorrect Transducer Type has been entered into PressureMAP for the device.

In the example above, there is probably a discrepancy between the way the device was installed in the field and the TD Type entered. In this case, the device was actually hooked up with the Ring side to Ground, but the TD Type may have been coded as Tip side to Ground. The appropriate Transducer Type for a typical flow transducer would be RF/RG-(range); the correct TD Type for a pressure transducer would be RP/RG-PSI.

Similarly, a SHRT reading for a resistive device on a subscriber pair may require a correction to the device's TD Type in PressureMAP data.

Troubleshooting Contactors

If a contactor or contact alarm is not reading correctly (indicating PAIR), 90 percent of the time the reason is inaccurate data. In PressureMAP, the types of readings generated for contactors are PAIR, NSE (noise), VOLT, BUSY, OK and ALRM. The NORM field of the data entry editor specifies whether the device operates in the OK condition when it is open or closed, or if it's a 540/270K ohm device, whether it should read 540K ohms or 270K ohms as a normal reading.

Analysis:

1. If a contactor reading is inaccurate, first confirm what type of device you have. Is it normally open or normally closed? Then make sure that this information is correctly input into PressureMAP. One way to check how the device is suppose to react to an alarm is to run a Realtime Reading Test from the 289H LSS Diagnostics Menu while someone temporarily shuts down the equipment being monitored (e.g., an air dryer). If the device does not go into alarm, confirm that you are testing the correct pair by having someone short it, or check the data entry editor to make sure the entry in the NORM field represents the type of device installed.

   You can also run a Leakage Test while someone shuts down the monitored device. What you should see is 10M ohms in both the Tip/Gnd Ohms and Ring/Gnd Ohms columns, and a switch from 540K ohms to 270K ohms (or vice versa) when the equipment is shut down. If the contactor is a binary type, you'll see a change from a "normally open" reading value greater than 100K ohms to one closer to 1K ohms.

2. A NSE reading on a contactor device indicates the presence of AC voltage on the monitoring pair. When this condition occurs, check for voltage by running the AC Test.

Conversion Charts
The information in the following charts is helpful when troubleshooting monitoring devices both in the field and via the 289H LSS Diagnostics feature. Notice that the first three charts provide conversions from milliamperes to the corresponding device reading value. The final two provide equivalent information for resistive devices.