An adjustable deadband pressure switch lets the set and reset points be moved independently across the entire sensor range, while a fixed deadband switch locks that gap by spring force, diaphragm stiffness, and microswitch plunger travel [S3]. On the datasheet level the difference shows up as a stated differential range (e.g. ADPS 3-30 psi or 10-80 psi) versus a single fixed value that the buyer cannot trim in the field [S5].
Deadband is defined as the pressure span between the rising setpoint and the falling resetpoint, expressed in the same units as the process variable [S2]. It is sometimes called hysteresis, and it exists in every mechanical pressure switch because the spring-and-pushrod mechanism cannot trip and re-trip on the exact same pressure value [S3]. For more background on switching fundamentals, see the pressure switch encyclopedia entry.
How the Two Deadband Types Behave on the Bench
A fixed deadband pressure switch has its gap defined by the rigidness of the diaphragm, the force of the spring, and the travel range of the microswitch plunger, so the value is set at the factory and cannot be tuned in the field [S3]. The buyer instead picks a catalog model whose fixed gap matches the expected process swing, accepting that the gap may drift slightly as the spring ages or as the diaphragm takes a set over thousands of cycles.
An adjustable deadband switch uses two independent set knobs: one for the rising (cut-in / cut-out) pressure and one for the falling reset pressure [S5]. On the Potter ADPS the minimum deadband is reachable at any point in the operating range, and a pressure change greater than the high setting repositions the snap-action switch to open or close a single SPDT contact [S4]. SOR's explosion-proof adjustable deadband line uses the same independent-knob concept to widen the gap on purpose, reducing on/off frequency and protecting compressors from short-cycling wear [S9].
Selection Criteria: Five Numbers You Pull from the Datasheet
The five figures that decide between fixed and adjustable are: (1) operating pressure range, (2) adjustable deadband window (or fixed deadband value), (3) proof pressure / burst rating, (4) electrical rating of the contact, and (5) housing/enclosure rating [S4][S5][S8]. The Potter ADPS datasheet lists 15 A at 125 VAC and 8 A at 250 VAC on a single snap-action switch, with a -4 F to 180 F media-temperature window, 1/2 in. NPT male process connection, and a NEMA 4X die-cast aluminum body [S4].
A representative general-purpose / adjustable deadband datasheet (ITM 2WPS0206F4F201) quotes 1% accuracy with die-cast aluminum construction and a welded seal, and it explicitly lists both fixed and adjustable deadband options for the same form factor [S8]. That dual-offering pattern is the practical answer to the spec question: choose the SKU whose adjustable window covers your process swing, and only drop to fixed deadband when the cycle count, proof pressure, and cost ceiling are all modest. For adjacent process measurement context, the pressure measurement overview covers the sensor side, while pressure gauge covers the local-indication counterpart.
Comparison Matrix: Fixed vs Adjustable on Five Decision Criteria
On cycling frequency, an adjustable deadband switch lets the user widen the gap to limit compressor starts per hour, which directly extends motor and contact life [S9]. The fixed deadband type forces the designer to oversize or undersize the process swing instead. On commissioning time, a fixed deadband unit ships set to a published value and needs only a setpoint knob, while the adjustable type requires two-knob calibration but allows in-field re-tune after the first 90 days of operation [S2][S5].
On cost, fixed deadband electromechanical switches are the lower unit price, and they dominate in OEM volume applications such as HVAC receiver tanks and small compressor unloaders. On proof pressure, the two are usually equivalent because the housing and diaphragm are shared; the ITM datasheet, for example, offers both modes in the same die-cast aluminum body at 1% accuracy [S8]. On explosion-proof and hazardous-area service, the adjustable deadband type dominates the SOR catalog (model 6NN/12NN/18NN families) because field-tuning is critical when the switch is locked inside a flameproof enclosure [S9]. For integration with electronic control, an adjustable switch is often paired with a pressure sensor signal in the same loop, while a fixed switch is typically a standalone electromechanical interlock.
Who It Is For, Who It Is Not For
Adjustable deadband is the right call for pump and compressor control, HVAC staging on chilled-water and boiler loops, and any application where the process swing is known only after start-up [S4][S5][S9]. It is also the right call in explosion-proof housings where the field engineer cannot swap internal springs every time the setpoint changes [S9].
Fixed deadband is the right call for low-cost OEM volume (refrigeration receivers, small air compressors, residential water pumps), for interlock-only logic where the gap is irrelevant, and for installations where a set-and-forget device is mandated by a simplified commissioning procedure [S2][S3]. It is the wrong call when the process pressure has a wide dynamic range, when short-cycling will damage the driven equipment, or when the installation is in a hazardous area where re-entry to adjust the gap is expensive [S9]. Field calibration in those cases is one of the strongest arguments for the adjustable architecture, and the pressure calibrator reference outlines the dead-weight test method used to verify both set and reset points in service.
Standards, Sourcing, and a Hazardous-Area Caveat
Pressure switches used in hazardous areas must be selected against the appropriate zone classification and gas group, and the explosion-proof housing itself is the protection method, not the deadband adjustment [S9]. The Ashcroft engineering guidance notes that the deadband applies to every mechanical pressure switch in every application, and that the gap is rooted in the physics of the spring-and-pushrod actuator, not in electronics [S3].
On the sourcing side, the 2026 catalog still treats the adjustable deadband ADPS as a current Potter Electric Signal SKU, with NEMA 4X rating, 1/2 in. NPT male connection, and the same 15 A / 8 A contact rating that has shipped for years [S4][S5]. When the same form factor needs to be specified with a fixed gas detector interlock or a flameproof cable entry, the ATEX cable gland selection map gives the matching accessory logic, while the barrier gland vs standard gland comparison covers the sealing decision for the conduit entry on the same enclosure. Two trackable signals to watch: OEM datasheets that begin publishing the deadband value as an adjustable range instead of a single number, and IIoT-style solid-state switches that replace the mechanical deadband with a software-set hysteresis window in the same NEMA 4X footprint [S2][S4].