We are looking to maintain a closed system at a slightly negative pressure compared to atmospheric (circa 500 Pa). What we’re trying to do is monitor the pressure difference between a closed air flow system and the surrounding air.
We’re trying to make sure that if there is an imbalance in the air flows in / out of the closed system, that the imbalance is such that air would flow inwards. We usually aim for 300 – 500 Pa negative and generally surrounding air will be slightly lower pressure than atmospheric. It doesn’t strictly have to be a differential, but that seems a better approach than using two absolute monitors and comparing. For the response time, I’m specifically talking about time to correctly measure the pressure.
We have had absolute pressure sensors before where we have changed the pressure effectively instantly and the sensor slowly reports pressure changing (every second) until it eventually stabilises at the new lower pressure. This can take anything up to 45 seconds and that’s way too long. Ideally, we want something that would be able to stabilise readings at the correct pressure within a second. We typically aim to maintain negative pressure in our system, but positive spikes are known, so we would want the sensor to be bidirectional as well with a range of -20 to +20 mbar?
The absolute pressure sensors approach is not recommended because you will be using a large range (~100,000 Pa) to measure a small difference (~500 Pa), and adding together the uncertainties of 2 sensors as well, so you end up with a very inaccurate pressure reading, unless you use a very expensive high accuracy barometric device, which will also most likely have a slower response time. The DMD341 has response time of less than 5 milliseconds, and will measure the difference between the closed system and the surrounding air in both directions.
DMD 341 Air DP Sensor
- SKU ID: s1-dmd341-0005
- Part No: 330-S020-3-G-TA0-Q00-6-000
- Differential Pressure Range: -20 to +20 mbar
- Output Signal: 0-10Vdc (3 wire)
- Accuracy: 2% FS
- Electrical Connection: Cable outlet with 2m PVC cable
- Process Connection: G1/8 female
- Media Compatibility: Non-aggressive gases and compressed air