Difference Between True and Calculated Wet-to-Wet Pressure

When running a comprehensive energy management system, the pressure sensors contained within are crucial for success. If these components aren't working properly, they could lead to more significant failures and expensive problems down the line. Depending on your setup, you'll likely use a variety of sensors, including dry-to-dry, wet-to-wet, and wet-to-dry.

Wet-to-wet sensors can be broken down further into two separate options: true pressure and calculated pressure. Because these sensors are deployed inside chillers, pumps, pressurized systems, and other essential systems, it pays to know the difference between them. So, let's look at how each pressure sensor works and how they differ.

What is True Wet-to-Wet Pressure?

True wet-to-wet pressure sensors are the most commonly used within the industry because they're the most accurate. With this system, both sides of the sensor are connected to a single diaphragm that moves in either direction, depending on where the pressure is heading. Because this setup uses a single connecting piece, the readouts are precise. One side affects the other, so there's almost no chance of interference or human error causing problems with the system.

Because true W/W sensors are the most accurate, they're often utilized in sensitive areas like flow measurement systems, pressurized tanks, and liquid level measurements.

What is Calculated Wet-to-Wet Pressure?

In this setup, both sensors operate independently of each other. However, they're both connected to the same pipe and oriented based on how pressure moves throughout the system. For a calculated wet-to-wet pressure sensor to work, one side has to be calibrated for high pressure while the other is calibrated for low pressure. Typically, each sensor can be programmed to detect pressure levels between 1 and 250 PSID. This way, you don't have to purchase separate sensor models to make the system work correctly.

Because calculated W/W sensors must be calibrated and can only work in one direction, they're far less precise and reliable than true W/W systems. Also, there's always a chance that one or both sensors weren't calibrated correctly based on the system they're monitoring. If this happens, the sensor won't be able to detect any potential problems and notify workers accordingly.

What are the Differences Between Each Measurement and How to Choose

As you can imagine, there are several key distinctions between each measurement system. Let's look at those differences and discuss when to choose one over the other.

• Precision - True W/W systems are far more accurate and precise because they just measure pressure and don't have to be calibrated beforehand.
• Complexity - Because true W/W sensors use one diaphragm, the setup is extremely simple and easy to deploy. If you're going to use calculated W/W sensors, you have to know how to calibrate them. Even worse, if one side isn't calibrated correctly, the whole system is unreliable.
• Reliability - When you have multiple pieces working independently, there's a greater chance that something could break or fail. With a true W/W sensor, either the entire device works or it doesn't. In a calculated W/W system, you may not realize there's a problem until it's far too late to fix it.

Overall, you want true wet-to-wet pressure sensors in high-value areas where speed and accuracy are essential. Also, this sensor type can work well for systems where the pressure may fluctuate unexpectedly, as it will detect differentials no matter what.

A calculated wet-to-wet pressure sensor is mostly beneficial for systems where pressure only flows one way, and there is little variation between readings. Otherwise, if you don't calibrate each sensor correctly, it could reach its limit before measuring the differential. When this happens, you'll see skewed results that aren't accurate.

One example of where this kind of sensor can work is when monitoring a pump's supply and return rates. Since you know what the range is for the pump already, it's much easier to set up each sensor.