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2-4.Current and voltage equipment

Current and voltage equipment

About current and voltage equipment

Azbil’s SDC series temperature controllers and indicating controllers have a function to input current and voltage.

As a device that outputs current and voltage to measure temperature, an infrared radiation thermometer is well known.
The temperature is measured using infrared rays emitted when the object naturally radiates heat.

The radiation thermometer uses a thermopile array of semiconductor elements.
Since the thermopile array cannot be directly input to the temperature controller or indicator controller, it is converted to current output or voltage output via an amplifier.

Measuring something other than temperature and trying to control it to an appropriate range requires a measuring instrument.
Measuring instruments are also called detectors, detectors, transmitters, detectors, sensors, and transmitters.
The current and voltage outputs are also collectively called analog outputs.

For example, to measure the height and distance of an object, a laser measuring device or an ultrasonic measuring device is used.
There are measuring instruments that measure everything, such as pressure, flow, speed, weight, clarity, sunlight intensity, sweetness, speed, power, magnetic field, and salt concentration.

The target value is compared with the actual value measured by the measuring instrument to determine whether it is excessive or insufficient, and the operation signal is turned ON / OFF or moved up and down.
That is the function (role) of the temperature controller and indicator controller.

In addition, temperature controllers and indicating controllers have the function of outputting current and voltage.
User can send current and voltage signals to other temperature controllers and indicating controllers while controlling userrself.

Features of 4-20mA signal

The most commonly used current input / output is 4-20mA.

① Voltage is not suitable for remote control because the voltage drops due to the resistance of electric wires and terminals (this is called voltage drop). In that respect, the current is the same everywhere, so accurate control is possible.

(2) Since the current does not change regardless of how many devices enter between, one current signal can be used by multiple devices.

③ Why is the halfway value of 4-20mA, because if it breaks, it becomes 0mA, so it can be distinguished from the controllable 0 value of 4mA.

④ The current signal can be converted to a voltage signal by interposing a resistor.
4-20mA can be easily converted to 1-5V.

⑤ Furthermore, since the maximum value is 20mA, there is an advantage that the equipment can be made small and inexpensive.

The following ranges can be input / output with the SDC15.
Input current 0 ~ 20mA, 4 ~ 20mA,
Input voltage 1-5V, 0-5V, 0-1V, 0-10V,
Output current 4-20mA,

The following ranges can be input / output with the SDC35 / 36.
Input current 0 ~ 20mA, 4 ~ 20mA,
Input voltage 1-5V, 0-5V, 0-10mV, 0-100mV, -10 ~ + 10m, V0-1V, 0-10V
Output current 4-20mA,
Output voltage 1-5V, 0-5V, 0-10V,

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