Connecting Current Loop Inputs; Connecting Current Loop Inputs To Thermocouple Channels - Data Translation TEMPpoint DT9871U User Manual

Connecting Current Loop Inputs

In some applications, such as solar cell, fuel cell, and car battery testing applications, you may
want to accurately sense and measure current in a high voltage loop.
TEMPpoint, VOLTpoint, and MEASURpoint instruments provide channel-to-channel
isolation of ±500 V, meaning that each input can be referenced to ±500 V.
The way you connect current loop inputs depends on the channel type you are using. This
section describes how to connect current loop inputs to thermocouple input channels, RTD
input channels, and high voltage input channels.

Connecting Current Loop Inputs to Thermocouple Channels

Thermocouple input channels on the DT9871U and DT9874 have an input range of ±0.075 V.
Therefore, you can use a 1 Ω series resistor to measure ±0.075 A. Similarly, you can use a 0.1 Ω
series resistor to measure ±0.75 A.
Thermocouple input channels on the DT9871 have an input range of ±1.25 V. Therefore, you
can use a 1 Ω series resistor to measure ±1.25 A. Similarly, you can use a 0.1 Ω series resistor to
measure ±12.5 A or a 10 Ω series resistor to measure ±0.125 A.
Figure 16 shows how to wire your signals to measure a current loop. In this example, the input
is referenced to ±80 V.
Note: On the standard DT9874 instrument, channels 0 to 15 correspond to the thermocouple
input channels.
Wiring Signals
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