Differential Pressure Switch (AI-32)
A mechanical differential pressure switch for cleanroom pressure control, isolation room monitoring, HVAC filter monitoring, and airflow applications. When the pressure reaches your setpoint, the contact changes state and your alarm, panel, BMS, or HVAC equipment responds.
A dependable alarm or interlock signal, not a continuous reading
The AI-32 is a mechanical differential pressure switch for cleanroom pressure control, isolation room monitoring, HVAC filter monitoring, and airflow applications. When the differential pressure reaches a preset switching point, it changes the state of an electrical contact, so connected alarms, panels, BMS systems, or HVAC equipment can respond.
It suits situations where you need a dependable alarm or interlock signal rather than a continuous pressure reading. The setpoint is adjusted in the field on a calibrated scale, and a transparent cover protects the setting. The IP54 enclosure suits cleanroom anterooms, gowning areas, and mechanical spaces.
From pressure difference to electrical signal
Two hose connections carry the high and low pressure sides to the switch.
A mechanical sensing element reacts to the pressure difference. No electrical power is needed for sensing.
When the differential pressure reaches the set point, the electrical contact changes state.
The connected alarm, BMS, PLC, panel, or HVAC interlock reads the change and acts on it.
The switch works for both positive and negative pressure rooms, depending on how the connections and setpoint are configured.
Built for controlled environments
Mechanical Switching, No Power for Sensing
Sensing does not depend on an electrical supply
Field Adjustable Setpoint
Set on the integral calibrated scale during commissioning or requalification
Transparent Protective Cover
The setting stays visible but is protected from accidental or unauthorized changes
IP54 Protection
IP54 with the cover fitted (IP00 without cover), suited to anterooms, gowning areas, and mechanical spaces
Multiple Ranges
30-300 Pa standard. Other ranges up to 1000-5000 Pa, available on request
Air and Non-Corrosive Gas Compatible
Suited to standard cleanroom and HVAC conditions
Continuous Duty Design
Built for permanent installation in pharmaceutical, healthcare, laboratory, and industrial facilities
Compact Installation
Fits AHUs, ducts, and cleanroom wall penetrations without major retrofit work
Where the AI-32 is used
Cleanroom Pressure Cascade Monitoring
Confirms the pressure relationship between adjoining rooms, corridors, airlocks, or gowning areas, and alarms when the threshold is crossed
Isolation Room Pressure Alarms
Monitors negative (infectious) and positive (protective) rooms against the corridor
Operating Theatre and ICU Monitoring
Confirms controlled hospital spaces hold their set pressure relationship
HEPA and Terminal Filter Blockage
Signals when filter pressure drop reaches the chosen level so maintenance can be planned
AHU Filter Monitoring
Gives a maintenance signal for bag and panel filters
Fan Status and Airflow Proving
Detects loss of expected pressure difference from fan failure or reduced airflow
Airlock and Gowning Room Verification
Confirms correct pressure staging
BMS, PLC, and Alarm Panel Integration
The contact output connects to these systems as a normal or alarm state
HVAC Safety Interlocks
Provides a switching signal for fan, damper, and ventilation alarm circuits, provided the load is matched
Pressure switching for data centers
In data centers, differential pressure switches work as basic safety interlocks or alarm triggers, while transmitters suit continuous, automated control.
Raised Floor Plenums
Signals when the positive air pressure that pushes cold air through the floor tiles drops below the setpoint
CRAC and CRAH Air Filters
Placed across filters and cooling coils, it triggers a maintenance light or alarm when the filter gets too dirty
Hot and Cold Aisle Containment
Confirms the pressure gap between hot and cold zones stays balanced, so servers do not pull in warm exhaust air
Trusted across regulated and critical facilities
Choosing the right type of instrument
Use the AI-32 for a simple, dependable alarm or interlock. Choose a monitor or transmitter when operators need to see or trend the actual pressure value.
| Parameters | Differential Pressure Switch (AI-32) | Differential Pressure Monitor | Differential Pressure Transmitter |
|---|---|---|---|
| Main function | ON/OFF switching at a set pressure | Continuous reading with display and alarms | Continuous signal sent to a controller |
| Output | Electrical contact | Display, with alarm or signal outputs depending on model | Analog signal such as 4 to 20 mA or 0 to 10 V |
| Display | No live pressure display, setpoint shown on scale | Shows the live pressure value | Usually none |
| Power for sensing | Not required | Required | Required |
| Best use | Alarms, interlocks, filter blockage alerts, fan proving | Room pressure display and logging at the point of use | Trending and control through a BMS or PLC |
Selecting the right range
The AI 32-03 with a 30-300 Pa range is our standard model. All other ranges are available on request. The ranges are typical starting points only, so confirm the final choice against facility design pressures and the filter manufacturer's final pressure drop. For low setpoints, choose the smallest range that covers the value so the setting sits comfortably on the scale.
| Application | Typical working pressure | Suggested starting range |
|---|---|---|
| Cleanroom pressure cascade | About 10 to 30 Pa between adjacent rooms | 30-300 Pa (standard) |
| Airlocks and gowning rooms | Low differential between stages | 30-300 Pa (standard) |
| Hospital isolation rooms | Low differential against the corridor | 30-300 Pa (standard) |
| HEPA and terminal filter blockage | Depends on filter final pressure drop | 200-1000 Pa or 500-2500 Pa, on request |
| AHU bag and panel filter monitoring | Depends on filter class and final pressure drop | 100-1000 Pa or 200-1000 Pa, on request |
| Fan status and airflow proving | Depends on fan and duct static pressure | 200-1000 Pa up to 1000-5000 Pa, on request |
| Non-standard requirement | Any | Custom range on request |
AI-32 pressure range
Standard model: 30-300 Pa. Other ranges up to 1000-5000 Pa, available on request.
| Model | Pressure Range | Differential | Tolerances |
|---|---|---|---|
| AI 32-02 | 20-200 Pa | 10 Pa | ≤ ±15% |
| AI 32-03 | 30-300 Pa (standard) | 10 Pa | ≤ ±15% |
| AI 32-04 | 40-400 Pa | 20 Pa | ≤ ±15% |
| AI 32-05 | 50-500 Pa | 20 Pa | ≤ ±15% |
| AI 32-10 | 200-1000 Pa | 100 Pa | ≤ ±15% |
| AI 32-25 | 500-2500 Pa | 150 Pa | ≤ ±15% |
| AI 32-11 | 100-1000 Pa | 50 Pa | ≤ ±15% |
| AI 32-50 | 1000-5000 Pa | 250 Pa | ≤ ±15% |
Straightforward to install
Pressure ports
Connect the high pressure port to the higher pressure point and the low pressure port to the reference point.
Placement between rooms
Take one sensing point from each side of the wall, door, or airlock. For filters, connect across the upstream and downstream sides.
Tubing
Use suitable hose, keep runs short, avoid kinks and trapped moisture, and route both lines similarly.
Location
Mount where the scale and cover are visible, away from strong vibration.
Electrical connection
Wire the contact to the alarm, BMS, PLC, or control circuit, matching the switching load.
After installation
Set the switching point on the scale and check the response against your commissioning procedure.
Technical specifications
Other ranges available on request, see the pressure range table above
Supports regulated facilities
The AI-32 is designed and manufactured by Ace Instruments, an ISO 9001:2015 certified manufacturer. It is intended to support facilities working to standards such as ISO 14644, EU GMP Annex 1, HTM 03-01, and ASHRAE 170. Final setpoints must follow each facility's own design and qualification requirements.
Frequently asked questions
1. What is the AI-32 Differential Pressure Switch?
The AI-32 is a mechanical differential pressure switch for cleanroom pressure control, isolation room monitoring, HVAC filter monitoring, and airflow applications. It changes the state of an electrical contact at a preset pressure point.
2. How is a differential pressure switch different from a monitor?
A switch is for on/off switching and alarms. A monitor or transmitter shows or trends the actual pressure value.
3. Why is a pressure switch useful in a cleanroom?
It gives an immediate electrical signal when pressure relationships move beyond the set point.
4. Can it monitor a cleanroom pressure cascade?
Yes. It can monitor the pressure between adjoining rooms, corridors, airlocks, or gowning areas and alarm when the threshold is crossed.
5. Can it monitor both positive and negative pressure rooms?
Yes, depending on how the connections and setpoint are configured.
6. Can it be used for HEPA filter blockage detection?
Yes. Filter pressure drop rises as the filter loads, so the switch can signal at a chosen level so maintenance can be planned.
7. Can it detect loss of airflow from an AHU or fan?
Yes. It can serve as a fan status or airflow proving device by detecting loss of the expected pressure difference.
8. Can it be used for hospital isolation rooms?
Yes. It suits positive and negative pressure isolation rooms, operating theatres, and ICUs.
9. How is the switching pressure adjusted?
In the field, on the integral calibrated scale, without a separate manometer. A transparent cover protects the setting.
10. Does it need an external power supply?
No. Sensing is mechanical. Power is only needed for the connected equipment.
11. Can it be connected to a BMS?
Yes. The contact output connects to BMS, PLC, alarm panels, or HVAC controls as a normal or alarm state.
12. Can it directly control a fan or damper?
It provides a switching signal for a suitable control circuit, provided the load is matched to the equipment.
13. What pressure ranges are available?
The standard range is 30-300 Pa. Other ranges up to 1000-5000 Pa are available on request.
14. What range is normally suitable for cleanrooms?
Pharmaceutical cleanrooms often run about 10 to 30 Pa between adjacent rooms, but the setpoint must follow the facility's design. Choose the smallest range that covers the value. The 30-300 Pa standard range suits most cascades.
15. What type of pressure connection does it have?
Two hose connections for the high and low pressure sides. Correct connection matters for the intended switching action.
16. Is it suitable for continuous operation?
Yes. It is designed for continuous duty. Routine tubing inspection and setpoint checks are recommended.
17. Does it require regular calibration?
Setpoint checks should be periodic, with the frequency based on the criticality of the application and the facility's quality program.
18. What happens when cleanroom pressure falls below the setpoint?
The contact changes state, which can trigger an alarm, warning light, BMS input, PLC, or interlock.
19. Can it be used in airlocks and gowning rooms?
Yes. It can verify pressure relationships in these cascade spaces.
20. What media can it measure?
Air and clean, non-corrosive gases.
21. Is it protected against dust ingress?
Yes. It is IP54 with the cover fitted (IP00 without cover), which suits cleanroom anterooms, gowning areas, and mechanical spaces.
22. What are the main applications?
Cleanroom alarms, cascade monitoring, filter monitoring, fan status, airflow proving, isolation room monitoring, and HVAC interlocks.
23. Which industries commonly use it?
Pharmaceutical, biotechnology, hospitals, laboratories, electronics, semiconductor, data centers, medical device manufacturing, food processing, and HVAC.
24. How do I choose the right configuration?
Base it on the normal operating differential pressure, required switching point, application, range, connections, and the control system used.
25. Why choose the AI-32 for cleanroom pressure switching?
Mechanical switching, field adjustable setpoints, a calibrated scale, compact size, IP54 protection, and compatibility with air and non-corrosive gases.
26. Which differential pressure switches can it be cross-referenced with?
Range-matching references include Siemens QBM81, Dwyer 1910/1900, Johnson Controls P233A, and Honeywell EDPS and DPS series. These are range-matching references only, not certified equivalence. Ace Instruments is not affiliated with or endorsed by those brands.
Need help choosing?
Tell us your pressure range, setpoint, and application and our engineers will recommend the right AI-32 configuration.
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