DIY Calibration of an Inclined Manometer

Standard manometers can help calibrate inclined manometers.

Manometers are used to measure pressure differences between two separate atmospheres. Commonly employed in HVAC or plumbing installations, an inclined manometer measures very slight differences, usually in the range of only 1 inch of water column. With a standard vertical manometer you can easily calibrate your more sensitive inclined manometer to ensure it is giving you the most accurate results. Vertical manometers measure pressure in increments of many inches of water column, or the amount of pressure needed to push or pull water at one atmosphere from another. Inclined meters are more sensitive, and are used to measure only slight differences.

Things You'll Need

• Vertical manometer
• Known pressure source and gauge (pump)
• Paper and pen

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Instructions

1. Examine the fluid level of your two manometers while at atmospheric pressure. Both manometers should have a fluid level at the 0 (zero) mark before connecting them to another pressure source. If the fluid level is not at the 0 mark while the test side of the manometer's tube is disconnected, fluid should be added or removed as necessary.

2. Calibrate and check for proper functionality of your vertical manometer by connecting a known functioning pressure source or pump to the test tube on your vertical manometer. Output 1 psi of pressure with the pump, which should correspond to 27.71 inches of water column rise on the vertical manometer's scale.

3. Connect the loose ends of both the inclined and the vertical manometer to the same pressure source you wish to measure. This should be a relatively low pressure source with a difference no greater than 1 inch of water column (about 0.036 psi).

4. Examine the increase in pressure that both manometers register. The vertical manometer will have several increments of 1 inch of water column, while the inclined meter will only have one 1 inch increment, broken down into fractions of an inch. Take note of when the vertical meter's indicating fluid level reaches the 1/2 inch water column mark, and the 1 inch mark, and compare these readings with that of the inclined meter.

5. Mount the inclined manometer on to a sheet of paper, and make an indicating mark of the 1/2 inch and 1 inch water column as read by the vertical meter. If the inclined meter varies by more than 1/8 of an inch from the readings of the vertical meter you will need to adjust the increments on the inclined meter's scale to reflect these measurements.

Tips & Warnings

• Check for any damage or leaks around the plugged end of your two manometers before testing.

References

• The Engineering Toolbox; U-Tube Manometer
• Toronto University; Manometers
• Webref; Manometer Calibration