Process Instrumentation
Pressure Switch Deadband and Setpoint: How to Configure Them Correctly
A pressure switch setpoint is the pressure at which the switch contact trips. The deadband is the pressure gap between the trip point and the reset point.
Both must be correctly calculated and set together — not independently.
A wrongly configured pressure switch setpoint causes either contact chattering or an unacceptably long reset delay. This guide covers the pressure switch setpoint calculation procedure with worked examples.
Trip Point and Reset Point
Chattering Prevention
High vs Low Pressure Switch
Adjustable Deadband
The most common pressure switch setpoint and deadband configuration mistake is setting the deadband too small.
A switch tripping at 10 bar and resetting at 9.9 bar will chatter if the process pressure oscillates ±0.2 bar around the setpoint.
The deadband must always exceed the normal pressure fluctuation at the trip point.
Pressure Switch Setpoint and Deadband: Key Definitions
Hello! Today we are covering the pressure switch setpoint and deadband — two parameters that are often set incorrectly because engineers focus on the trip point without thinking about the reset behaviour. Getting both right is essential for stable, reliable switching. Let us go through the definitions, the calculation method, and several worked examples for high-pressure and low-pressure switch applications.
A pressure switch setpoint and its paired deadband together define two critical pressure values that define its behaviour.
The trip point (also called the setpoint or switch point) is the pressure at which the contact changes state.
The reset point is the pressure at which the contact returns to normal. The difference between them is the deadband.
Core relationship
High-pressure switch (trips when pressure rises):
Trip point: pressure rises to → contact changes state
Reset point = Trip point minus Deadband
(pressure must fall below the reset point before the contact resets)
Low-pressure switch (trips when pressure falls):
Trip point: pressure falls to → contact changes state
Reset point = Trip point plus Deadband
(pressure must rise above the reset point before the contact resets)
Trip point: pressure rises to → contact changes state
Reset point = Trip point minus Deadband
(pressure must fall below the reset point before the contact resets)
Low-pressure switch (trips when pressure falls):
Trip point: pressure falls to → contact changes state
Reset point = Trip point plus Deadband
(pressure must rise above the reset point before the contact resets)
Did You Know? The deadband is sometimes called the "reset differential" or "hysteresis" in manufacturer data sheets.
All three terms describe the same thing: the pressure gap between the trip point and the reset point. However, "hysteresis" is technically the more general term (it describes any system where the output depends on the history of the input, not just the current value).
In process instrumentation, all three terms are used interchangeably and mean exactly the same thing for a pressure switch. See the deadband guide, the pressure switch guide, and the pressure switch vs transmitter guide for related concepts.
All three terms describe the same thing: the pressure gap between the trip point and the reset point. However, "hysteresis" is technically the more general term (it describes any system where the output depends on the history of the input, not just the current value).
In process instrumentation, all three terms are used interchangeably and mean exactly the same thing for a pressure switch. See the deadband guide, the pressure switch guide, and the pressure switch vs transmitter guide for related concepts.
Trip point
Pressure at which the switch contact changes state (actuation)
Reset point
Pressure at which the contact returns to its original state (deactuation)
Deadband
= |Trip minus Reset|
Always positive. The gap that prevents chattering on a noisy pressure signal.
3× rule
Deadband must be at least 3 times the peak-to-peak pressure fluctuation at the trip point
Why the Deadband Matters: Chattering and Reset Delay
A pressure switch with a deadband too small for the process pulsation will chatter.
See the zero shift guide for how repeated chattering-induced mechanical stress causes zero drift in transmitters.
Chattering means the contact rapidly opens and closes as process pressure oscillates across the trip point.
Each transition generates a spark at the contact, accelerating wear. A switch rated for 100,000 cycles can fail within hours if it chatters at 10 Hz on a pulsating pump discharge.
Tip: The 3× rule for deadband sizing.
Measure or estimate the peak-to-peak pressure fluctuation at the location where the switch will be installed.
Set the deadband to at least 3 times this fluctuation. If the pressure oscillates by ±0.3 bar (0.6 bar peak-to-peak), the deadband must be at least 1.8 bar (3 × 0.6).
For pump discharge service with severe pulsation, measure the pulsation with a data logger before specifying the deadband. Pulsation amplitude on reciprocating pump discharge lines can exceed 20% of the mean pressure.
Measure or estimate the peak-to-peak pressure fluctuation at the location where the switch will be installed.
Set the deadband to at least 3 times this fluctuation. If the pressure oscillates by ±0.3 bar (0.6 bar peak-to-peak), the deadband must be at least 1.8 bar (3 × 0.6).
For pump discharge service with severe pulsation, measure the pulsation with a data logger before specifying the deadband. Pulsation amplitude on reciprocating pump discharge lines can exceed 20% of the mean pressure.
A deadband that is too large creates a different problem: the switch trips but does not reset for a long time after the process condition has cleared.
On a high-pressure trip at 10 bar with a 5 bar deadband, the switch does not reset until pressure falls below 5 bar.
If normal operating pressure is 8 bar, the switch can never reset automatically. An operator intervention or manual reset is required.
Did You Know? Mechanical pressure switches have a fixed deadband determined by the spring and cam geometry inside the switch body.
The deadband is factory-set and typically ranges from 1 to 15% of the switch's full-scale range. A 0 to 100 bar switch might have a fixed deadband of 2 to 8 bar.
Electronic pressure switches (with an electronic trip comparator) allow the deadband to be freely programmed — typically from 0.1% to 30% of the calibrated span. This programmable deadband is one of the main advantages of electronic over mechanical pressure switch designs.
The deadband is factory-set and typically ranges from 1 to 15% of the switch's full-scale range. A 0 to 100 bar switch might have a fixed deadband of 2 to 8 bar.
Electronic pressure switches (with an electronic trip comparator) allow the deadband to be freely programmed — typically from 0.1% to 30% of the calibrated span. This programmable deadband is one of the main advantages of electronic over mechanical pressure switch designs.
How to Calculate the Pressure Switch Setpoint and Deadband Correctly
The pressure switch setpoint calculation follows four structured steps.
The trip point must be set with enough margin from normal operating pressure to avoid nuisance trips.
The deadband is then set to ensure stable, non-chattering operation.
Step-by-step: High-pressure switch setpoint calculation
Step 1: Define the process danger pressure (PDP) — the pressure at which damage or hazard begins.
Step 2: Define the normal operating pressure (NOP) — the steady-state or maximum normal pressure.
Step 3: Calculate the available margin: Margin = PDP minus NOP
Step 4: Set the trip point = NOP + (Margin × 0.7)
(this places the trip at 70% of the available margin above NOP, leaving 30% for the protective action)
Step 5: Measure peak-to-peak pulsation (ΔP_pp) at the installation point.
Step 6: Set deadband = maximum of (3 × ΔP_pp) and (0.05 × trip point)
(5% of trip point is the typical minimum deadband for mechanical switches; use whichever is larger)
Step 7: Verify reset point = Trip point minus Deadband is above NOP.
If reset point ≤ NOP, the switch will never auto-reset during normal operation. Increase the margin or reduce the deadband.
Step 2: Define the normal operating pressure (NOP) — the steady-state or maximum normal pressure.
Step 3: Calculate the available margin: Margin = PDP minus NOP
Step 4: Set the trip point = NOP + (Margin × 0.7)
(this places the trip at 70% of the available margin above NOP, leaving 30% for the protective action)
Step 5: Measure peak-to-peak pulsation (ΔP_pp) at the installation point.
Step 6: Set deadband = maximum of (3 × ΔP_pp) and (0.05 × trip point)
(5% of trip point is the typical minimum deadband for mechanical switches; use whichever is larger)
Step 7: Verify reset point = Trip point minus Deadband is above NOP.
If reset point ≤ NOP, the switch will never auto-reset during normal operation. Increase the margin or reduce the deadband.
Worked Examples: Pressure Switch Setpoint and Deadband
Example 1: High-Pressure Trip on a Pump Discharge Line
Example 1 — High-Pressure Switch
Process: Centrifugal pump discharge, water service
Normal operating pressure (NOP): 8 bar
Maximum allowable working pressure (MAWP): 16 bar
Measured pulsation: ±0.15 bar (0.30 bar peak-to-peak)
Step 1: Available margin = 16 minus 8 = 8 bar
Step 2: Trip point = 8 + (8 × 0.7) = 8 + 5.6 = 13.6 bar → round to 14 bar
Step 3: Deadband from pulsation = 3 × 0.30 = 0.90 bar
Step 4: Deadband minimum (5% of trip) = 0.05 × 14 = 0.70 bar
Step 5: Use deadband = 1.0 bar (round up from 0.90 bar)
Step 6: Reset point = 14 minus 1.0 = 13.0 bar
Step 7: 13.0 bar > 8 bar (NOP) → auto-reset is possible ✓
Final: Trip at 14 bar. Reset at 13 bar. Deadband = 1 bar.
Normal operating pressure (NOP): 8 bar
Maximum allowable working pressure (MAWP): 16 bar
Measured pulsation: ±0.15 bar (0.30 bar peak-to-peak)
Step 1: Available margin = 16 minus 8 = 8 bar
Step 2: Trip point = 8 + (8 × 0.7) = 8 + 5.6 = 13.6 bar → round to 14 bar
Step 3: Deadband from pulsation = 3 × 0.30 = 0.90 bar
Step 4: Deadband minimum (5% of trip) = 0.05 × 14 = 0.70 bar
Step 5: Use deadband = 1.0 bar (round up from 0.90 bar)
Step 6: Reset point = 14 minus 1.0 = 13.0 bar
Step 7: 13.0 bar > 8 bar (NOP) → auto-reset is possible ✓
Final: Trip at 14 bar. Reset at 13 bar. Deadband = 1 bar.
Example 2: Low-Pressure Trip on a Cooling Water Supply
Example 2 — Low-Pressure Switch
Process: Cooling water supply to a heat exchanger
Normal operating pressure (NOP): 4.5 bar
Minimum safe pressure (equipment needs at least): 2.0 bar
Measured pulsation: ±0.05 bar (0.10 bar peak-to-peak)
Step 1: Available margin = 4.5 minus 2.0 = 2.5 bar
Step 2: Trip point = 4.5 minus (2.5 × 0.7) = 4.5 minus 1.75 = 2.75 bar → round to 2.8 bar
Step 3: Deadband from pulsation = 3 × 0.10 = 0.30 bar
Step 4: Deadband minimum (5% of trip) = 0.05 × 2.8 = 0.14 bar
Step 5: Use deadband = 0.30 bar
Step 6: Reset point = 2.8 plus 0.30 = 3.1 bar
Step 7: 3.1 bar less than 4.5 bar (NOP) → auto-reset is possible ✓
Final: Trip at 2.8 bar. Reset at 3.1 bar. Deadband = 0.3 bar.
Normal operating pressure (NOP): 4.5 bar
Minimum safe pressure (equipment needs at least): 2.0 bar
Measured pulsation: ±0.05 bar (0.10 bar peak-to-peak)
Step 1: Available margin = 4.5 minus 2.0 = 2.5 bar
Step 2: Trip point = 4.5 minus (2.5 × 0.7) = 4.5 minus 1.75 = 2.75 bar → round to 2.8 bar
Step 3: Deadband from pulsation = 3 × 0.10 = 0.30 bar
Step 4: Deadband minimum (5% of trip) = 0.05 × 2.8 = 0.14 bar
Step 5: Use deadband = 0.30 bar
Step 6: Reset point = 2.8 plus 0.30 = 3.1 bar
Step 7: 3.1 bar less than 4.5 bar (NOP) → auto-reset is possible ✓
Final: Trip at 2.8 bar. Reset at 3.1 bar. Deadband = 0.3 bar.
Tip: Verify setpoint with a calibrated pressure source after adjusting any mechanical switch.
Mechanical pressure switches have a set screw or adjusting knob with a scale that may not be accurate — scale markings are for guidance only, not precision.
After adjusting, apply pressure slowly from below the trip point and record the exact pressure at which the contact changes state using a calibrated pressure gauge and a continuity meter. Do this three times and take the average. The spread between the three readings tells you the repeatability of the switch — specification is typically ±1 to ±2% of full scale range.
Mechanical pressure switches have a set screw or adjusting knob with a scale that may not be accurate — scale markings are for guidance only, not precision.
After adjusting, apply pressure slowly from below the trip point and record the exact pressure at which the contact changes state using a calibrated pressure gauge and a continuity meter. Do this three times and take the average. The spread between the three readings tells you the repeatability of the switch — specification is typically ±1 to ±2% of full scale range.
Did You Know? The IEC 61511 standard for safety instrumented systems (SIS) requires that the trip setpoint of a safety-rated pressure switch be verified at the required proof test interval — not just at commissioning.
For a pressure switch in a SIL 1 safety instrumented function with a proof test interval of one year, the trip pressure and reset pressure must be checked annually and recorded in the instrument maintenance management system.
The allowable deviation between the verified trip pressure and the nominal setpoint is typically ±3% of full scale range or ±the manufacturer's specified repeatability, whichever is tighter in the relevant design basis document.
For a pressure switch in a SIL 1 safety instrumented function with a proof test interval of one year, the trip pressure and reset pressure must be checked annually and recorded in the instrument maintenance management system.
The allowable deviation between the verified trip pressure and the nominal setpoint is typically ±3% of full scale range or ±the manufacturer's specified repeatability, whichever is tighter in the relevant design basis document.
Pressure Switch Setpoint Calculator
Setpoint and Deadband Calculator
Enter process conditions to calculate the recommended trip point, reset point, and minimum deadband
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Watch: How to Adjust a Pressure Switch Setpoint
Pressure Switch Setpoint: High vs Low Switch Comparison
| Parameter | High-Pressure Switch | Low-Pressure Switch |
|---|---|---|
| Trips when | Pressure rises above the trip point | Pressure falls below the trip point |
| Reset point location | Below the trip point (reset point = trip minus deadband) | Above the trip point (reset point = trip plus deadband) |
| Auto-reset condition | Process pressure must fall below the reset point | Process pressure must rise above the reset point |
| Trip point calculation | Trip = NOP + (0.7 × available margin above NOP) | Trip = NOP minus (0.7 × available margin below NOP) |
| Deadband minimum | Maximum of: 3 × peak-to-peak pulsation, and 5% of trip point | Same formula — always use the larger value |
| Deadband too small | Contact chatters as pressure oscillates across trip point | Same failure mode |
| Deadband too large | Reset point may be below normal operating pressure, preventing auto-reset | Reset point may be above normal operating pressure, preventing auto-reset |
| Typical applications | Overpressure protection, high-pressure alarm, pump relief bypass | Pump cavitation protection, filter clog alarm, low supply pressure alarm |
Pressure Switch Setpoint FAQ
What is the pressure switch setpoint?
The pressure switch setpoint is the pressure where the contact changes state. A high-pressure switch trips when pressure rises above it. A low-pressure switch trips when pressure falls below it.
What is the deadband of a pressure switch?
The deadband is the gap between trip and reset points. For a switch at 14 bar with a 1 bar deadband, the reset point is 13 bar. This prevents chattering.
Why does a pressure switch chatter?
Chattering happens when the deadband is smaller than the pressure fluctuation at the trip point. As pressure oscillates, the contact cycles rapidly. Set the deadband to at least 3 times the peak-to-peak pulsation.
How do I set the deadband on a mechanical pressure switch?
Most mechanical switches have a factory-fixed deadband from the spring geometry. Check the data sheet for the fixed value. For a programmable deadband, use an electronic switch.
What is the difference between trip point and reset point on a pressure switch?
The trip point is where the contact changes state. The reset point is where it returns to normal. For a high-pressure switch, the reset point is always lower.
External References
- How to Adjust a Pressure Switch: Switch Point and Deadband | NOSHOK (2024)
- Pressure Switch Selection: Setpoint and Hysteresis | WIKA (2025)
What We Learn Today
- The pressure switch setpoint is the trip pressure value. The reset point is the pressure at which the contact returns to normal. The deadband is the gap between them — it must be at least 3 times the peak-to-peak pulsation to prevent chattering.
- For a high-pressure switch: trip = NOP + 70% of available margin. Reset = trip minus deadband. Confirm the reset point stays above normal operating pressure to allow auto-reset.
- Verify the actual trip and reset pressures with a calibrated source after any adjustment. Mechanical switch scale markings are guidance only — not precision calibration references.
“Setting only the trip point and ignoring the deadband is like setting an alarm clock without checking whether it can turn itself off. The switch will trip correctly — and then chatter or stay tripped indefinitely, depending on which way you got it wrong.”