dataTaker DT80 - Page 310

UM-0085-B09 DT80 Range User Manual Page 310
RG
R4 – 2-Wire Independent Resistance Inputs
Note: This configuration is not available on DT80/81 Series 1 loggers.
No lead resistance compensation is possible with this configuration (other than by using the channel factor)
In Series 4, this configuration is not suitable with excitation III
A 2-wire measurement can also be made by connecting the resistance to * and # only. This frees up the + and –
terminals for a separate independent measurement. For example, vibrating wire strain gauges often incorporate a
thermistor temperature sensor. This wiring configuration would allow the gauge to be connected to + and – and the
thermistor to * and #.
Figure 135: Wiring for 2-wire independent resistance input
To measure
Use the command
R
1*R
R5 – Series 3 and 4 2-Wire Resistance Inputs
Note: These configurations are only available on Series 3 and 4 loggers
For these configurations, the excitation is fixed at 200μA (I). The II channel option is invalid.
In Series 4, these configurations is not suitable with excitation III
Series 3 and 4 models can direct excitation to either the *, + or – terminal. This allows 2-wire resistance measurements
to be made between the + and –, * and #, + and # or – and # terminals.
Use the
2W channel option to select these types of measurements.
Figure 136: Wiring for 2-wire independent resistance input (Series 3 and 4)
To measure
Use the command
R
1R(2W)
Figure 137: Wiring for 2-wire shared terminal resistance inputs (Series 3 and 4)
To measure
Use the command
R1
1*R(2W)
R2
1+R(2W)
R3
1-R(2W)
These measurements can be useful for detecting open circuit sensors. For example, the following will force an invalid
reading to be logged if a vibrating wire strain gauge is detected as open circuit:
1FW(=1CV,W)
IF(1R(2W)>5000){1CV=99999}
1CV("freq")