Simulators of environmental state sensors are used to set up and control the efficiency of automatic process control systems. In some cases, it is convenient to use a voltage-resistance converter with an optoelectronic output module based on a controlled photoresistor as a simulator of potentiometric sensors.
 An optical-electronic voltage-to-resistance converter, which has a galvanic isolation of the output and has a linear characteristic in a given range of output resistance is developed. The developed converter allows to set the angular and free coefficients of the linear equation arbitrarily that describes the response function of the converter and correctly simulate the operation of a potentiometric state sensor of the controlled parameter. An operating model of the converter was developed and manufactured, experimentally determination of its response function for different values of the free coefficient, supply voltage and different options for the circuit design of the optoelectronic module was carried out.
 The principle of operation of the converter is based on a change in the resistance of photoresistors under the influence of optical radiation coming from a controlled source. The model of the converter consists of optical and electronic blocks. The optical block consists of an optical radiation source and two photoresistors simultaneously directed at it. The signal from one photoresistor is the output, and the signal from the second photoresistor is analyzed by the control circuit, which synchronously changes the illumination on the light-sensitive areas of the photoresistors through the brightness controller in accordance with the voltage level of the control and corrective signals.
 The experimentally determined response function of the converter in the initial section has a non-linearity in the zone of low input voltages, which is determined, foremost, by the limitation of the lamp brightness and depends on the scheme of its inclusion. The non-linearity zone in the researched converter can be significantly reduced by increasing the supply voltage. Within the given range of change of the output resistance of the rectilinear section of the response function, the output resistance of the converter is linearly related to the input voltage, according to the results of experimental measurements in natural laboratory conditions, the conversion error hasn’t exceeded 0.3%.