Column: Optical isolation


Figure 2: The module’s connections supply VPS


A 27V TVS is chosen for a 24V external power . For VPS


≥ 24V, this TVS must be


replaced with an appropriate one. For example, when VPS


= 36V, a 39V TVS must be used.


Setup and calibration Here we assumed that VIN


(VIN Figure 3: IOUT vs VIN for the module Remote connections to current


transmitters can sometimes be subjected to voltage surges. Therefore, it is prudent to limit the maximum surge voltage applied to the XTR116 as low as practically possible. A 27V TVS (Transient Voltage Suppressor) is used to filter and suppress any transients coming from the current input and output terminals.


is taken from the DAC


output of a 5V microcontroller with 0.00V ≤ VIN


≤ 5.00V. When 0.00V ≤ VIN


and therefore output current range IOUT


/0.25)mA. Input voltage range VIN = 0-20mA; see Figure 3.


≤ 5.00V, IOUT = = 0-5.00V Table 1 provides some example input voltages


and output currents for this signal converter module, with its prototype circuit board shown in Figure 4. To calibrate it, do the following: = 250Ω.


1. VPS = 24V and RL 2. Set VIN P1 make VTP1 VIN


to +5.00V and, then, by adjusting = +5.00V.


3. By adjusting P2 make sure that when VIN


= 0.00V, VRL = +5.00V, VRL


= 0.00V and, also, when = +5.00V.


Table 1: Modules 1 and 2 example voltages, assuming 0.00V ≤ VIN


≤ 5.00V


Figure 4: The module’s prototype circuit board


www.electronicsworld.co.uk March 2023 13


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