202K Series — Electronic Pressure Switch

202K Digital Pressure Switch, Dual Relay + 4-20 mA Output

Electronic pressure switching from -0.1 to 100 MPa with a 4-digit LED display, two programmable relay outputs, optional 4-20 mA analog output, IP65 protection, and a rated switching life of more than 1,000,000 cycles.

100 MPa
Max Range
±0.5% FS
Accuracy
1M+
Switching Cycles
IP65
Protection
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HMK 202K electronic pressure switch with 4-digit LED display and M12 connector

What Is the 202K Electronic Pressure Switch?

The 202K is an electronic pressure switch with display, built around an oil-filled piezoresistive sensor and a microcontroller-driven switching logic board. Unlike a mechanical diaphragm-and-spring switch, the 202K measures pressure continuously, drives a 4-digit LED readout, and triggers two independent SPDT relay contacts whenever the process value crosses a user-set threshold.

Setpoints, hysteresis bands, and switching delays are configured through a four-button front-panel menu — not by turning a screw. An optional 4-20 mA analog output lets the same device act as both switch and transmitter, feeding a PLC or DCS in parallel with local relay control.

Typical buyers use the 202K on hydraulic power units, water and wastewater pumps, HVAC chillers, compressed-air lines, injection-molding machines, and test benches — anywhere a team needs on-device pressure visibility without wiring a separate indicator.

202K Technical Specifications

GroupParameterValue
Pressure inputRange-0.1…0 MPa up to 0.01…100 MPa
ReferenceGauge or absolute
Overpressure / Burst1.5× / 3× FS
AccuracyCombined accuracy≤ ±0.5% FS
Long-term stability≤ ±0.5% FS / year
Response time< 10 ms
Display & OutputDisplay4-digit 0.36″ LED, -1999…9999, plus 2 status LEDs
Switch output2× SPDT relay, load < 24 V / 1.2 A
Analog output (optional)1× 4-20 mA, 2-wire
Switching life> 1,000,000 cycles
Power & EnvironmentSupply24 VDC ± 20%, < 3 W
ConnectionM12 industrial connector
ProtectionIP65
Ambient / Media temp-25…+70 °C / -25…+85 °C

Key Features of the 202K Digital Pressure Switch

4-Digit LED Readout

Real-time process value on-device; no HMI or laptop required for operator visibility.

Dual Programmable Relays

AL1 and AL2 each have independent setpoint, hysteresis or window band, and delay settings.

Optional 4-20 mA Output

Specify suffix RA to add loop-powered analog signaling in parallel with relay switching.

Password-Protected Menu

Default password 0001 prevents accidental setpoint drift in shared work cells.

Oil-Filled Piezoresistive Core

Stable to ≤ 0.5% per year, shock- and vibration-tolerant, ranges up to 100 MPa.

Million-Cycle IP65 Rating

Field-grade reliability with M12 quick-disconnect connector for simple replacement.

Where the 202K Is Used

Hydraulic Power Units

Trip pumps on clogged filters or start a stand-by circuit when pressure drops below working range.

Water & Wastewater Pumps

Start/stop booster pumps, cycle duty/standby pairs, and prevent dry-run on intake manifolds.

HVAC & Chiller Plants

Supervise chilled-water and condenser loops with visible PV and programmable deadband.

Compressed-Air Headers

Switch compressors on pressure band, with AL2 as a high-pressure interlock for safety.

Injection Molding

Monitor clamp and injection circuits with repeatable setpoint — critical for cycle quality.

Test Benches & OEM

Hybrid switch-and-transmitter in one unit reduces BOM lines and simplifies calibration.

Dimensions, Wiring & Installation

The 202K uses a compact stainless housing with a flush front face for the LED window. Process connections available: G1/4, G1/2, NPT1/4, NPT1/2. Electrical connection is a 5- or 8-pin M12 on the top face, simplifying cabinet routing.

Wiring rule summary: 24 VDC and common on pins 1/2, relay 1 (COM1/NO1/NC1) on pins 3/4/5, and relay 2 (COM2/NO2/NC2) on pins 6/7/8 for the 8-pin variant. On the RA analog variant, the 4-20 mA loop shares the 24 V supply in 2-wire mode. Mount vertically where possible; avoid installing at the lowest point of a line that traps condensate.

202K Ordering Code

Format: 202K-[Range]-[Process]-[Output]-[Accuracy]

SegmentCodeMeaning
RangeP01 / 10 / 100 / 1000-0.1…0 / 0…1 / 0…10 / 0…100 MPa (full list on request)
ProcessG14 / G12 / N14 / N12G1/4, G1/2, NPT1/4, NPT1/2
OutputR / RADual relay only / Dual relay + 4-20 mA
Accuracy0.5±0.5% FS

Example: 202K-10-G14-RA-0.5 = 0…1 MPa range, G1/4 process connection, dual relay with 4-20 mA analog, ±0.5% FS accuracy.

202K Electronic Pressure Switch FAQ

An electronic pressure switch uses a silicon or piezoresistive pressure sensor plus a microcontroller to open or close a relay when pressure crosses a configurable setpoint. Compared to a mechanical switch — which relies on a spring and a diaphragm — an electronic switch offers a digital readout, field-adjustable setpoints, tighter repeatability, and typically a longer switching life.

Process pressure acts on an oil-filled stainless isolation membrane. The piezoresistive bridge inside the sensor generates a mV signal proportional to pressure; the internal MCU converts this to engineering units, displays the value on the 4-digit LED, and drives the AL1/AL2 relays based on the configured setpoint, hysteresis, and delay.

Pick electronic when you need on-device readout, software-adjustable setpoints, diagnostics, or a high switching-cycle life above one million cycles. Mechanical switches remain viable for simple, isolated, low-cost on/off duty where no display or reconfiguration is required. The 202K also covers the hybrid case via its 4-20 mA option — one device serves as both switch and transmitter.

Enter the menu with the front button, type password 0001, then navigate AL1H (setpoint) → AL1F (hysteresis or window band) → AL1D (delay). Repeat with AL2 for the second relay. Confirm with END. All settings persist through power cycles.

EEoo, EEo1, EEo2, EE11, and EE22 are internal diagnostic codes for sensor open/short, ADC fault, and relay-driver self-check failures. The full code table is printed in the 202K manual supplied with each unit; for any EE code that persists after a power cycle, contact HMK support.

Yes — specify the RA suffix in the order code. The analog output is 2-wire, loop-powered, and runs in parallel with the two relay outputs so the device works as both a switch and a transmitter.

Ready to Order 202K Electronic Pressure Switches?

Our pressure product engineers can help you select the correct range, process connection, and output option for your application. Send us the pressure media, working pressure, required accuracy, and signal interface — we will respond with a configured 202K order code, datasheet, and lead time.

Our engineers typically respond within 12 business hours with detailed technical specifications and pricing.

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