Down ranging a pressure transducer or a digital pressure gauge means that a sensor is selected with a higher pressure range, and the manufacturer calibrates the output to match the desired application pressure range.
As a cautionary note, this results in reducing the sensor resolution, and if too low, it will affect the performance accuracy of the sensor. That said, we are careful to discuss this with our customers to ensure we stay within an acceptable range.
How far to down range a sensor is completely subjective. However, the application pressure range is typically 75% of the full-scale range of the sensor. Following this rule-of-thumb will generally keep you out of trouble.
There are a few examples of when down ranging is a good idea:
First, if frequent bursts or spikes in pressure can occur beyond the application pressure range, then it could be advantageous to down range the sensor. In general sensors less than 10K psi have a 2X over pressure protection and a 5X burst rating or 20K PSI – whichever is less.
Let’s say you have an operating rang of 500 psi, but occasional spikes could go to 600 psi. Though the spikes would fall in the 2X over pressured protection range, using a 1000 psi sensor that has been down ranged to 500 psi would give the protection needed, without the sensor actually being over pressured. This will help keep the sensor calibration stable and not shorten the life of the sensor due to constant over-pressure.
For the same reasons, it may also be a good idea if the pressure is at or near maximum most of the time.
Second, if a sensor requires a custom calibration other than what is offered by the manufacturer, the sensor is most likely to be down ranged. As stated, this can affect performance if you’re not careful. Make sure you discuss this with the manufacturer to understand what you’re getting.
For example, pressure sensors are generally offered in standard ranges. Sometimes a sensor needs to be manufactured with a non-standard full-scale range. In one case, a customer needed an 800 psi full scale output. We down ranged a 1000 psi unit to meet the customer’s need. This allowed us to save the customer time and money, and to get a reliable sensor to them much faster.
Let us know if you have questions about down ranging a pressure transducer. You can reach us at 888-525-7300, or you can send us an email to sales@apgsensors.com.
