PIE 311Plus Diagnostic RTD & Milliamp Calibrator

Ground Leak Detection

Have you ever replaced a “faulty” transmitter only to find the problem was somewhere else in the loop? And did you end up throwing the transmitter away after you fixed the other problem “just in case” the transmitter was faulty?

If you find a loop where the transmitter is calibrated correctly but all the readings elsewhere in the loop have a fixed offset this is due to a Zero Shift. This zero shift is typically caused by some current in the loop bypassing the transmitter. This might be caused by ground faults, moisture or corrosion.

If you have some loops that are erratic after it rains there may be moisture present in a junction box or where insulation has broken down. Turn on Ground Leak Detection and use the PIE 311Plus to power up the loop. Any current that isn’t controlled by the transmitter or other current control element will be indicated as leakage on the PIE 311Plus display.

The PIE 311Plus powers up the 2-Wire transmitter or loop and indicates the total current and the uncontrolled current. This provides information useful in troubleshooting loop errors.

Using Ground Leak Detection

The PIE 311Plus supplies a nominal 24 volts DC at 24 mA to the 2 Wire Transmitter or loop. The current passed by the transmitter will be accurately displayed by the PIE 311Plus along with an indication of leakage current on the display. If there is an uncontrolled loop, a transmitter with upscale burnout, bad or missing sensor or a short the display shows “OVER RANGE” and the red OVERLOAD LED will flash.

Note: Many installed transmitters will normally indicate 0.01 to 0.10 mA leakage without significant control problem. Unstable readings may indicate loose connections or the presence of moisture.

Typical Error Conditions

The PIE 311Plus is supplying the loop voltage. A calibrated transmitter is limiting the loop current to 12.00 mA. An additional 0.51 mA is not controlled by the transmitter and is leaking somewhere in the loop.

The PIE 311Plus is supplying the loop voltage. There is an control loop error. This may be a transmitter (set for upscale burnout) with a bad or missing sensor, or a short in the loop. The red ERROR LED will also flash.

Calibrate 2 Wire Transmitters

With LEAK DETECT enabled the 311Plus indicates when there is a ground fault in the loop or an internal problem with the transmitter allowing unregulated current to pass through causing offsets in the loop current.

Reading RTD Sensors

READ

Choose this function to measure temperatures with an RTD probe or sensor.

Calibrating RTD Instruments

SOURCE

Choose this function to provide a simulated RTD signal into controllers, temperature transmitters, indicators or any input devices that measure RTD sensors.

Troubleshooting RTD Sensors

Here is an example of the PIE 311Plus reading a sensor with all 4 wires connected.

Here is an example where connections are made to a 4 wire sensor and the 311Plus indicates that only Wires 1, 2 & 4 are connected. There may be a loose connection or a break in wire 3 somewhere between the sensor and the 311Plus.

This is much simpler and quicker than going through the process of testing each pair of wires to figure out which, if any, connection is loose or which wire is broken.