# Pneumatic signal & How to modify a transmitter?

Pneumatic Instrument

For industrial pneumatic devices, the most typical air pressure range is 3 to 15 PSI. The low end of the process measurement scale is represented by an output pressure of 3 PSI, while the high end is represented by an output pressure of 15 PSI.

If process pressure were to be applied to the preceding example of a transmitter calibrated to a range of 0 to 250 PSI, the transmitter would produce a 3 PSI air signal in the absence of process pressure and a 15 PSI air signal in the presence of process pressure. The unique “receiver” gauge would be labelled from 0 to 250 PSI, while the actual mechanism would function in the 3 to 15 PSI range emitted by the transmitter. The end-user need not be aware of the information’s transmission from the process to the indicator, similar to the 4-20 mA loop. The operator can once more see right through the 3-15 PSI signal medium.

Generally, a pressure value of 3 PSI corresponds to 0% of the scale, a pressure value of 15 PSI corresponds to 100% of the scale, and every pressure value between 3 and 15 PSI corresponds to a proportionate percentage between 0% and 100%.

The same 3–15 PSI air pressure signaling method has been used in the construction of pneumatic temperature, flow, and level control systems. In each instance, clean pressurized air is provided to the transmitter and controller at a specific nominal pressure (20 to 25 PSI, typically), and the instrument signal travels via tubing.

Why do we use 3 to 15 psi?

Since it is a relatively modest range of pressure that is simple to detect and manage, 3 to 15 psi (pounds per square inch) is frequently used in industrial applications. The 3 to 15 psi range is well-liked for the following reasons:

Accuracy: Maintaining accurate control over the pressure being applied is crucial in many industrial processes. A limited range of pressure enables more precise measurement and control.

Compatibility: A lot of pneumatic control systems, including those used in manufacturing, are created to function in this pressure range. This enables improved component compatibility and makes it simpler to integrate new equipment into current systems.

Safety: In industrial environments, using a low-pressure range can assist reduce accidents and injuries. A lower pressure range can assist lessen the likelihood of mishaps because high-pressure systems can be dangerous if not adequately controlled.

Cost: Lower pressure systems frequently need less expensive parts and can be less expensive to maintain over time.

Overall, the 3 to 15 psi pressure range is a feasible and effective pressure range for many industrial applications, providing a balance of accuracy, compatibility, safety, and cost-effectiveness.

How do I modify a transmitter’s 20 psi air supply?

A general process for changing a 20 psi air supply to a transmitter, but steps will vary depending on the type of transmitter and the particular arrangement needed:

Verify the manufacturer’s standards: To make sure the 20 psi air supply is within the appropriate range, it’s crucial to check the transmitter’s manufacturer’s specs before altering the air supply.

Attach the air supply: Using the proper connections, attach the transmitter to the 20 psi air supply.

Measure the current output: As soon as the air supply is turned on, use a suitable instrument, such as a multimeter, to measure the transmitter’s current output.

Adjust the air supply: The air supply should be adjusted until the transmitter’s current output is at the desired level. Depending on the starting pressure and the intended output, this may necessitate raising or lowering the pressure.

Monitor the output: Once the air supply has been adjusted, check the output of the transmitter to make sure it is stable and within the appropriate range. If the output is not within the desired range. If further air supply adjustments are required to get the output stable and within the required range, fine-tune as appropriate.