RHE21 Installation & Startup Guide – Doc. No. 8.2.1.04 – Ver. 1.31
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Figure 146: Digital Inputs
The digital input can be operated with an active DC signal instead of a switch. The maximum
input voltage must not exceed 30V DC. Note that inputs require a switching current of 0.6mA;
the minimum input voltage for a high reading is 14.4V DC.
3.2.3.4
Analog Input
The RHE21-E5 or RHE21-H3 can be equipped with a 4-20 mA analog input for connecting an
external transmitter (such as a pressure sensor) with a passive 4-20 mA output. The RHE21
transmitter provides power to the connected devices’ output.
The 4 – 20mA analog input is connected to terminal 60 (positive) and terminal 61 (negative) in
the bottom terminal box. It is highly recommended to use a shielded cable and that the shield is
connected to terminal 68 (PE) at the transmitter.
The analog input in RHE21 transmitters is certified for use with an external transmitter in a
hazardous area which includes a certified barrier circuitry for connection with an intrinsically safe
device.
The negative (AIG) terminal of the input is internally connected to PE, so it is important to connect
only devices that are floating.
Figure 17: Analog Input
Summary of Contents for RHE21
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