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Application notes
Low Pressure Gauges: When You Need To Go Low
When to Use
Bourdon tube pressure gauges have range limitations with the lowest range being 10 psi. Any time you need to measure below that range you will need a different sensing element. When you need to measure very low pressure or vacuum, low pressure gauges with a capsule design can measure as low as 1” H2O.
A capsule sensing element consists of two corrugated metal discs of brass or stainless steel fused together. A change in pressure will cause the discs to expand or contract, and this motion is transferred to the indicator through a pinion movement mechanism.
You can use this cost-effective gauge to measure low pressure very precisely with accuracies up to ±1.0%. The case size has a direct impact on accuracy. The capsule element is placed vertically inside the case of a low pressure gauge. The lower the measured pressure is, the larger the area of the diaphragm and the larger the case diameter.
A Variety of Applications
You can use a low pressure gauge for a variety of industries ranging from medical to HVAC to industrial applications (e.g., chemical/petrochemical, power stations, offshore, environmental technology and mechanical engineering). Typical product applications include, but are not limited to: fan and blower monitoring, filter monitoring, low pressure pneumatic systems, vacuum pumps, gas burners, medical suction devices and overpressure monitoring in cleanrooms.
When selecting materials for a low pressure gauge, you can choose brass for most applications but you will want stainless steel for aggressive media applications.
A Variety of Benefits
- Because you can use these instruments in a variety of industries, the benefits are diverse as well. Some of these advantages include:
- The capsule pressure gauge is 10 times overpressure safe as well as full vacuum safe. A special relieve valve is activated in positive or negative overpressure situations, protecting the capsule element.
- With a capsule design, you can have a clockwise pointer travel while measuring vacuum (with a Bourdon tube gauge you can only move counterclockwise). In these cases, the dial face must indicate “VACUUM.”
- The low pressure gauge comes standard with an external zero adjustment screw because certain operating conditions could cause the very sensitive capsule element to shift off zero.
- WIKA gauges in this category offer Swiss movement for precise accuracy.
- A non-magnetic version makes the low pressure gauge enticing for some fields (e.g., gauges are part of medical devices that stay with the patient during MRI procedures).
- The finely polished nickel-silver pinion gear and shaft of the movement ensure repeatable accuracy.
Because you must take many details into consideration when selecting low pressure gauges, WIKA’s technical advisors can help you identify and select the appropriate instrument for your specific application requirements.