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 […]

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Resistance Thermometer Current Loop Transmitter

Resistance temperature sensor (RTD, resistive temperature device)  comes in NTC (negative temperature coefficient) and PTC (positive temperature coefficient) forms. A schematic diagram below show a signal conditioner circuit for such thermometer. This sensor conditioning circuit works in current mode (current loop) and the amplifier inside gives a current output that is  inversely proportional with the sensor’s resistance. This temperature transmitter […]

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Precision Current Loop Thermocouple Transmitter

Current loop analog data transmission is used in industrial environment because of its robustness (good noise immunity), while providing wiring fault detection (short and broken wiring) with a simple mechanism by detecting out range current level. In 4-20mA current loop standard, the valid signal should be in the range of 4 to 20mA. Zero ampere current would indicate broken wiring, […]

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Optical Pyrometer Detect The Spectrum Composition

This pyrometer is used to measure an incandescent body. The principle for this measurement is that the hotter the body, the spectrum of the radiation will contain more shorter wavelength (visible light). This circuit use infrared filter to separate the visible and infrared spectrum, since the sensor (photodiode) is sensitive for both visible and infrared spectrum. Here is the schematic […]

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