Isolated Remote Temperature To Frequency Converter

The following circuit shown in the schematic diagram converts temperature reading (from +30° to +30° F) to its corresponding frequency (30 to 3000 Hz). Other benefit is that a 4N28 isolate the output to protect the receiver from dangerous interference. We can use this circuit diagram to send temperature information across long transmissions lines because the 4N28 output voltage can be selected, as required. We can adjust the scales using the total value of Rs (12 kΩ fixed and 5 kΩ variable). The output is 10 Hz/°F when Rs is set to about 14.2KΩ.