Hello everyone,

I am starting my experience with acquisition systems and, in particular, with dataTaker products, but I'm having some difficulties.

My main goal is to assemble a monitoring system using Carlson strain meters, thermometers and a joint foundation meter and I am using the DT85G Series 2 for this purpose. I believe DT85G Series2 is capable of measuring the resistance changes for those instruments since it is mentioned in the User's Manual (Strain Gauges – Carlson Meter, page 201: CS1 – 5 Wire Carlson Meter, CS2 – 4 Wire Carlson Sensor and CS4 – 3 Wire Carlson Sensor).

Although the manual's reference, I found some difficulties in applying these wirings and codes into the DeLogger. For example, a Carlson strainmeter is a four wire sensor and the code should be 1*R(II) 1R(4W,II) 1+R(II) for measuring M1, M2 and M3 and therefore calculate R1 and R2, but I could not build, with the options avaliable in Delogger, the same type of code.

The closest I could get was 1R(2W) 1R(4W) and 1+R(2W) but it didn't returned an answer. With this problem, I turn to direct connection to the dataTaker using Labview and the codes 1R(II) 1R(4W,II) 1+R(II) for each strainmeter.

The obtained results were compatible with I was expecting. Is there some way to use the Delogger using the codes available in the User's Manual? Another question relates to the values obtained for the Carlson strainmeter using the Labview.

I believe there is few experience with Carlson strainmeter and that the automatic acquisition is not easy since the resistance values are very small. When defining the Delogger's options for this kind of instrument (Resistance Wiring) there are notes about the 2-wire configurations.

The User's Manual says that 2-wire configurations only should be used where the unknown resistance is >500 Ohms. Since the our Carlson instruments uses resistances around 40-60 Ohms and since the measurement of M1 and M3 is using this kind of configuration (1*R... and 1+R...) it is not recommended for the use of this type of Carlson instruments.

Maybe I'm disregarding something that I don't know and I apologize is that is the case. Someone have experience or knowledge about this issue? Or is there a way to overcome this question?

Thank you.
Carlos Serra

Good morning Carlos,

The I and II channel options specify the current excitation level to use. In DeLogger they can be found under the Excitation column heading. Then assign the readings to a channel variable and use another channel to calculate the strain and temperatures

Cheers,
Roger