Stability is defined as a change (or lack of change) in accuracy over a period of time.
Drift is commonly used as a specification to illustrate the stability, or change in accuracy over a period of time, commonly shown as X%/year where X = a number; i.e. 0.25%/year. In this scenario, a device with a ±1% accuracy, would be expected to have an accuracy of ±1.25% (1%+0.25%) after a period of one year. Depending on the design, brand, and range of the sensing instrument, the stability can vary widely.
There are many benefits in utilizing sensors and instrumentation with great long-term stability.
Stability reduces out-of-calibration issues. If a measurement device drifts out of calibration, it can be measured incorrectly and risk exposure of personnel or patients to harmful microorganisms in pressure monitoring applications in healthcare settings.
HVAC SYSTEMS
Stability improves HVAC system performance by increasing overall efficiency and reducing the need for costly maintenance. If an air handler, VAV system, or chiller/boiler system is running inefficiently, components are more likely to wear and break down faster than in a more efficient system.
The reduction in downtime associated with maintenance and recalibration is another benefit of stability. Stability helps to ensure full production capacity and can be recalibrated on a scheduled date/time that corresponds to a plant shutdown/plant maintenance schedule.
Stability also ensures patient rooms are available and not out-of-calibration, which is especially useful in healthcare facilities with an above average patient capacity.
In critical environments, stability ensures safety standards are maintained.
SEMICONDUCTOR MANUFACTURING
If pressure, temperature, and relative humidity (RH) are not maintained properly in semiconductor manufacturing areas, it may result in infiltration of dust and particulates from not maintaining a proper differential pressure, a spike or drop in RH, or a change in temperature, which may damage products being manufactured.
PHARMACEUTICAL MANUFACTURING
Similarly, in pharmaceutical manufacturing and compounding areas, if these parameters are not maintained properly, infiltration of microorganisms from not maintaining a proper differential pressure, a spike or drop in RH, or a change in temperature could contaminate drug or provide unsuitable storage/manufacturing conditions.
HEALTHCARE FACILITIES
Lastly, the infiltration of viruses, bacteria, or pathogens from or into an isolation room, clean room, and/or operating room is key to maintaining patient and personnel health. Maintaining a proper differential pressure in these critical healthcare environments will help prevent the spreads of illnesses caused by infectious microorganisms.
HOW DWYER CAN HELP
The Dwyer Series DHC Digihelic® differential pressure controller provides a stability rating of less than ±1% full scale per year. The DHC is a 3-in-1 instrument offering a digital display gage, control relay switches, and a transmitter with both current and voltage outputs.
The Digihelic® controller is the ideal instrument for pressure, velocity, and volumetric flow applications reading in several commonly used engineering units with optional unidirectional or bidirectional ranges. These units achieve a 1.5% or better accuracy on extremely low ranges, and 0.5% accuracy for ranges at or above 1 in w.c.
If you have any questions, the DwyerOmega Applications Engineers are available to assist by phone at (219) 879-8868 x6402, or by email at tech@dwyeromega.com.