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# Pressure Switch

02/08/2017 5:53 AM

Hi

I am getting confused with Deadband and Differential range of pressure switch. Is this two term same or different??Searching explanation from experts.

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#1

### Re: Pressur Switch

02/08/2017 6:05 AM

The equipment manufacturer(s) is/are in the best position to advise on this question and most others:

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#6
In reply to #1

### Re: Pressur Switch

02/09/2017 8:45 AM

That's so 1960's. Perhaps it is time to switch to this icon?

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#2

### Re: Pressur Switch

02/08/2017 8:08 AM
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#3

### Re: Pressur Switch

02/08/2017 9:16 AM

Dead band is the difference between increasing and decreasing switch points. Differential is the difference in pressures from low pressure to high pressure. Probably could be defined as range of the unit.

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#4

### Re: Pressure Switch

02/08/2017 2:57 PM

Deadband is the difference between the 'trip' setpoint and the pressure at which the switch resets or changes state.

Common pressure switches have a fixed deadband range. Some pressure switches are available with adjustable deadband. The actual deadband is a function of design and how the mechanical tolerances match up.

A blog here describes the woes of fixed deadband (you're never sure what you're going to get out of the box):

Technically, hysteresis affect the deadband and switch setpoint, because pressure switch setpoints are spec'd as "on pressure rise/increase" or "on pressure fall/decrease". The difference is due to the mechanical hysteresis.

Differential

Differential is a two port pressure measurement where one port is the pressure reference.

All pressure measurement is inherently differential with a reference pressure, but the vast majority of pressure switches are gauge pressure, referencing atmosphere. There are very few absolute pressure switches that reference absolute zero.

A differential pressure switch has two ports, one port for high side pressure and one port for the low side pressure (the reference).

A gauge pressure switch has only one pressure port:

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#5

### Re: Pressure Switch

02/08/2017 6:20 PM

The term "differential" is used ambiguously in the industry. In some cases, such as "differential pressure switch", it is used as Iris's examples describe. However, for regular (one-port) pressure switches and thermostats, "differential" is frequently used as identical to "deadband"; i.e., difference between cut-out and cut-in points. In no case other than here have I ever seen it to mean allowable operating range.

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#7

### Re: Pressure Switch

08/07/2017 1:00 PM

I would have thought that Deadband refers more to a mechanical type of switch such as a pressure switch etc. on a compressor and is the region where it switches off and on again. Some switches have adjustable Deadbands to prevent say in the case of an air compressor, the electric motor motor constantly switching on and off which is bad for the motor and also the starter.

Differential I would have thought was more applicable to process controls where it is critical to maintain certain conditions for both safety and process considerations like maybe a furnace / cremator where you maybe detecting and maintaining a low negative pressure that is in the realms of millibars and the the controller is then typically going to be an electronic device that is capable of making minute adjustments all the time to keep that pressure constant.

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