A pressure gauge is a simple instrument, but an incorrect choice can provide a poor or misleading picture of the actual pressure.
Measuring range
The range should cover the expected pressure without normal operation being too close to zero or the end of the scale.
Accuracy
For low pressures, appropriate resolution is required. A pressure gauge with too large a scale may not show useful minor fluctuations.
Installation point
We must know if we are measuring before or after a regulator, filter, or valve, because each point provides different information.
Comparison
During diagnostics, two simultaneous measurements at different points are often more useful than a single reading.
