Negative pressure measurement--the zero-point issue of differential pressure transmitters
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The negative pressure inside the furnace of the heater is measured using an EJA differential pressure transmitter in the middle section, and a Siemens ST700 differential pressure transmitter at the top. The negative pressure measurement point is connected to the positive pressure measurement side; the negative pressure side is exposed to the atmosphere. The measurement range is -300 Pa to +300 Pa. It is appropriate for the output to be 12 mA when both the positive and negative pressure sides are exposed to the atmosphere, with 0% corresponding to this value. However, during zero calibration, it is necessary to use a pressure generator to apply a negative pressure of -300 Pa at the negative pressure measurement point before zero can be set. This process is time-consuming and labor-intensive. Is there a simpler way to perform zero calibration? Moreover, when the atmospheric pressure changes, the differential pressure also changes, resulting in slight deviations in the measurement values under the same operating conditions. Would it be more appropriate to use a single-flange diaphragm pressure gauge?
This post was last edited by myface on 2021-9-3 at 08:43. Adding a 300Pa value on the negative pressure side is already a very simple method. Do you really want to create a vacuum of -300Pa on the positive pressure side? What is the principle behind a membrane box pressure gauge? It is already under slight pressure, so it will definitely be quite sensitive to changes in atmospheric pressure.
This post was last edited by gaiyin47 on 2021-9-3 09:36. Can’t you indicate negative pressure by applying pressure on the negative-pressure side?
This is usually how it’s done; I was just wondering if there’s a simpler way
Zeroing the pressure gauge using negative pressure is also a common practice; I’m just wondering if there’s a simpler way. Did I write it wrong? Would it be better to use an absolute pressure gauge, as that would provide greater accuracy?
You need to consider the purpose of measuring the furnace pressure – it’s not meant to provide an accurate absolute pressure, but rather to determine the pressure difference with the outside atmosphere. In simpler terms, maintaining a negative pressure is necessary to prevent the fire from escaping.