In the photo below is a connection to a DT2011B data logger and a terminal block from a DT2040 and DT2055B data logger.
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The Red and Black wires are the coil connections for measureing the raw B Units. The Green and White wires are the thermistor connections for measuring the temperature. The bare wire is the shield connection, it is not required for the piezometer to be read by the data logger or the readout.
Below is the expected resistance readings from the specific wires. The coil connections are approximately 180 Ohms, but will depend on the length of the cable. The thermistor resistance will depend on the temperature and will match the thermistor temperature derivation table below as long as there is no short to another wire.
It a DT data logger CSV download, the raw values are on the right hand side of the document and the calculated values are on the left.
When measuring the resistance on the piezometer coil, remove the terminal block and put the mether leads on the red and black wires. The meter should be in the 200 Ohm range, if it does not read, check to see if you get a reading in the 2000 Ohm range.
Below is the thermistor temperature derivation table
Put the multimeter leads on the green and white wires with the multimeter on the 20,000 Ohm range.
The resistance reading should match the values in the raw readings with a data logger and they will give a representative temperature using the thermistor vs. temperature resistance table.
The meter is in the 20,000 Ohm range, but will still register a value in the 200k range. This value below is approximately 3810 Ohms which is about 19.6 C.
Check for a short to the shield from all the wires in the 20M Ohm setting, the reading should be an open circuit, but it is possible that if the operator is touching the leads, a resistance across the body can be read. Try avoid touching the with your hands, or use gloves.
The Meter should be set in the 20M Ohm range to look for short circuits, the dial can be turned down to get a more accurate reading if it is a ‘hard’ short circuit.
Below are the lead connections on the terminal blocks for checking between the shield and each of the wires. There should not be any connection between the red/black and the green/white wires are they are exclusive. It there is a connection between any of those wires, there is damage somewhere in the cable.
