The pressure range is the most complicated and confusing specification parameters to define for a pressure sensor. If you do not fully understand the different types of pressure that can be measured, you are likely to end up reading pressures inaccurately, or worse still, damaging the sensor before you have had a chance to correct the situation.
The two main questions that you need to ask yourself are, what is the range of pressure I need to measure over, and what baseline pressure will it be relative to?
If you are measuring the direct pressure of a gas or liquid process then you will need either a gauge (g, rel) or absolute (abs, a) reference pressure range depending on whether you need to track relative to atmospheric air pressure changes (zero output = atmospheric pressure) or measure independently of atmospheric pressure changes (zero output = perfect vacuum). This will define the baseline pressure required, and will dictate the type of pressure sensor needed, since typically a pressure sensor will be manufactured to only measure gauge or absolute pressure, and cannot be modified once it has been built.
- Gas supply 100 mbar static pressure transmitter for boiler room
- UPS-HSR USB Pressure Sensor with High Sample Rate Logging
- High sulphuric acid content resistant 16 bar g 4-20mA water pressure sensor
- Autoclave pressure sensor and display with 10 bar range
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- 33X High Accuracy Digital Output Pressure Sensor
- DMP331 Precision Pressure Transmitter
- 700 to 1100 millibar scaled 4 to 20mA output pressure sensor for barometric pressure measurement
- 300°C max temperature, 0 to 300 bar, high range pressure sensor
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If you are measuring pressure between two points such as either side of an extraction fan, or across a filter, then you will need a differential pressure (dp) sensor.
- DMD331 Compact Differential Liquid Pressure Sensor
- PD39X High Differential Pressure Transmitter
- DPS300 User Switchable Pressure Range, Volts or Current Output Low DP Sensor
- DPT200 Pressurised Tank Level Differential Pressure Transmitter
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Pressure ranges are typically specified by the manufacturer in bar (bar)or pounds force per square inch (psi) for medium to high pressures, and millibars (mbar), hectopascals (hPa), pascals (Pa) or inches of water column (inH2O, inWG, inWC) for low pressures. If your required pressure range is in other units then use a pressure converter to determine the pressure in common units.
It is important to think about the maximum pressure to be measured and the likely peak pressure that could be generated by the measured process. If there is a large difference between the two pressures then choosing a pressure sensor with a high overpressure rating to match the peak pressure is imperative to prevent calibration disturbance, mechanical damage or failure of the sensor.
Occasionally it is necessary to measure negative pressure or pressures below the baseline reference pressure. It is only possible to do this with a gauge reference or differential pressure sensor. For example you may want to measure suction or vacuum pressure which are pressures between full vacuum and atmospheric pressure. Another example of measuring negative pressure would be to apply a reverse the differential pressure across an air filter periodically, as a preventive maintenance measure to clean the air filter and improve air flow.
Negative pressure ranges can also be combined with positive pressure ranges to create a compound range or a bidirectional range. These can be used to combine vacuum and positive pressure ranges, or for measuring ventilation pressures in a duct where the air could be flowing in either direction.
- LEO3 Current or Digital Output Pressure Gauge
- DMP343 Low Range Pneumatic Pressure Sensor
- DMK457 Marine Approved Pressure Transmitter
- DMP457 Marine Approved Pressure Transmitter
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Liquid Head Pressure
It is also very common to use pressure sensors to measure liquid level by measuring the liquid head pressure. These pressure ranges are often specified in meters or feet of water column. Due to the variance in liquid density it is also possible to have specifically scaled ranges, for example 1.078 bar for a 10 metre high tank which contains a liquid of a slightly different density to water.
- Hydrostatic Level Sensors
- 25m borehole submersible pump level indicator and control switch with level sensor
- Modbus RTU RS485 submersible borehole water level sensor
- Low cost 2 metre high diesel tank level sensor with 0-10 volt output
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