How to Test a 4-20 mA Pressure Transducer?

Piezoelectric sensors are a device that uses the piezoelectric effect to measure the electrical potential caused by applying mechanical force to a piezoelectric material. Piezoelectric sensors are mostly used in flex motions, touch, vibrations, and shock measurement.

A pressure transducer is a device that measures the pressure of a fluid, indicating the force the fluid is exerting on surfaces in contact with it. Pressure transducers are used in many control and monitoring applications such as flow, air speed, level, pump systems or altitude.

1. Connect the positive terminal of the transducer to the positive terminal of the power supply.
2. Connect the negative terminal of the transducer to the positive lead on the multimeter.
3. Connect the negative lead of the multimeter to the negative terminal on the power supply.

A transducer receives sequences of high voltage electrical pulses called transmit pulses from the echosounder. Just like the stereo speakers at home, the transducer then converts the transmit pulses into sound. The sound travels through the water as pressure waves.

Transducers and transmitters are virtually the same thing, the main difference being the kind of electrical signal each sends. A transducer sends a signal in volts (V) or millivolt (mV) and a transmitter sends a signal in milliamps (mA).

As its name implies, the general purpose of a transmitter is to transmit signals. These signals contain information, which can be audio, video, or data. In essence, a transmitter launches signals into the air via a transmitting antenna.

All transducers, transmitters, and switches are sensors, but not all sensors are transducers, transmitters, or switches.

Pressure transmitters are divided into three types: Absolute Transmitter: This transmitter take vacuum pressure as its base, and then measures process pressure. Gauge Transmitter: This type measures process pressure with the location’s atmospheric pressure as a base.

Pressure Sensors: Millivolt (mV) output signal (also a general term for all pressure types); a device that measures pressure. Pressure Transducers: High level voltage or frequency output signal including 0.5 to 4.5V ratiometric (output signal is proportional to the supply), 1-5V and 1-6kHz.

The potentiometer is also called as pots and it one of the most commonly used devise for measuring the displacement of the body. The potentiometer is the electrical type of transducer or sensor and it is of resistive type because it works on the principle of change of resistance of the wire with its length.

Disadvantages of Potentiometer

• The use of Potentiometer is inconvenient.
• The area of cross-Section of potentiometer wire must be uniform which is practically not possible.
• During experiment the temperature of potentiometer wire must remain uniform.
• The major disadvantage is that it requires a large force to move their sliding contacts i.e. wiper.

The potentiometer is used as a voltage divider in the electronic circuit. The potentiometer is used in radio and television (TV) receiver for volume control, tone control and linearity control. The potentiometer is used in medical equipment. It is used in wood processing machine.

Both devices use digital input signals to set an analog output. Digital potentiometers allow you to adjust an analog voltage, while DACs adjust current, voltage, or both. Potentiometers have three analog connections: the high connection, the wiper (or analog output), and a low connection (Figure 1a).

The principle of a potentiometer is that the potential dropped across a segment of a wire of uniform cross-section carrying a constant current is directly proportional to its length. The potentiometer is a simple device used to measure the electrical potentials (or compare the e.m.f of a cell).

Switches and Push Buttons are commonly used as input devices for digital system. LED is commonly used as a simple Digital output device. Usually on Digilent Board, a high voltage will light it up and a low voltage will shut it down.

Variable resistors and potentiometers each augment the standard resistor symbol with an arrow. The variable resistor remains a two-terminal device, so the arrow is just laid diagonally across the middle. A potentiometer is a three-terminal device, so the arrow becomes the third terminal (the wiper).

Instead they are used to adjust the level of analog signals (for example volume controls on audio equipment), and as control inputs for electronic circuits. For example, a light dimmer uses a potentiometer to control the switching of a TRIAC and so indirectly to control the brightness of lamps.

After measuring total resistance turn the pot to midrange and measure the resistance between the wiper and an end. If it’s about 50% of the total resistance it’s a linear pot, if it’s about 10% or 90% of the total resistance it’s a logarithmic pot.

There are two main types of potentiometer, linear potentiometers and rotary potentiometers. Membrane Potentiometers are another type of potentiometer they are often referred to as “soft pots” and can be either linear or rotary.

It is calculated as V/L, where V is the potential difference between two points and L is the distance between two points. Also K = (IρL/A)/L = Iρ/A. E1/E2 = L1/L2 is the equation to compare the emf of two cells, where E1 and E2 are the emf and L1 and L2 are the length at which it is balanced.

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The maximum voltage is limited by the Wattage rating. If the potentiometer is rated at 1 Watt, you can only apply a maximum of 100 volts. I.e 10 mA. That applied to the voltage across the full 10000 ohms.