When you have a question about process automation that needs a short answer, let us know with #WishIknew and @Visaya! We’ll reply with a #WishIknew post. It’ll give a quick explanation, then some related articles, videos, or reviews if you want to know more.
I wish I knew how to calibrate a manometer!
Good question! My first job in the field had me doing manometer calibration. Even these simple devices need a little know-how to make them right.
First, you should know the difference between manometer calibration and adjustment, if you don’t already. We have a bunch of articles on Visaya discussing this difference and other similar topics. You can read some of them here, here or here.
To calibrate, you need a reference device with a higher accuracy than the device under test. You can use a digital pressure transmitter or even another manometer, as long as it has better accuracy.
Basically, you need to check the measuring range of the manometer under test against the reference device to see if it still falls within an acceptable error margin. To do that, you need to ramp your pressure up and down through the measuring range. Usually, we do 0, 25, 50, 75, and 100 percent.
If your manometer doesn’t measure within your error limits, then you can adjust either the zero or the span. You may need a pointer extractor, so make sure you have that before you begin if you need it.
To adjust the zero, you may need to remove the parts of the manometer, but only enough to get access to the pointer. For the span, you need to tweak the angular adjustment slots at the bottom of the manometer. Before removing anything, you should mark the o, 25, 50, 75, and 100 percent of the manometer’s measuring range.