Model 522 Family, Rolling Diaphragm Type Differential Pressure Indicators
Aluminium Body and Stainless Steel Body
Model 522 OEM Indicators (Rolling Diaphragm)
Rolling diaphragm DP gauge/switch; compact, weather resistant; DIN plug‑in switch option; 2½” & 4½” dials; working pressure up to 1,000 PSIG (6,900 kPa); 5 year warranty. Full scale accuracy ±5% (0–5 PSID to 0–50 PSID). Avoid reverse pressure.
Model 555A Tri‑Colour Dial (Diaphragm)
Diaphragm tri‑colour filter indicator; two‑sided dial; no switch option; 1 year warranty; body in glass filled nylon; working pressure up to 300 PSIG (2,070 kPa); full scale accuracy ±5%.
Model 522C Tri‑Colour Dial (Rolling Diaphragm)
Model 522C: Rolling diaphragm with tri‑colour dial (Clean / Change / Dirty); 2½” dial only; DIN plug‑in switch option; 1 year warranty; same pressure/accuracy class as 522.
Other Body Material: Acetal plastic
Rolling diaphragm DP gauge/switch; compact, weather resistant; DIN plug‑in switch option; 2½” & 4½” dials; working pressure up to 1,000 PSIG (6,900 kPa); 5 year warranty. Full scale accuracy ±5% (0–5 PSID to 0–50 PSID). Avoid reverse pressure.
Model 555A Tri‑Colour Dial (Diaphragm)
Diaphragm tri‑colour filter indicator; two‑sided dial; no switch option; 1 year warranty; body in glass filled nylon; working pressure up to 300 PSIG (2,070 kPa); full scale accuracy ±5%.
Model 522C Tri‑Colour Dial (Rolling Diaphragm)
Model 522C: Rolling diaphragm with tri‑colour dial (Clean / Change / Dirty); 2½” dial only; DIN plug‑in switch option; 1 year warranty; same pressure/accuracy class as 522.
Other Body Material: Acetal plastic
Model 522 2.5 Inch Dial
Model 522
Product Features and Benefits
- Simple rolling or convoluted diaphragm design (model dependent)
- Glass reinforced thermoplastic dial case (panel mountable)
- Weather resistant and corrosion resistant (specific configurations) — NEMA 4X where stated
- Shatter‑resistant lens
- Plug‑in DIN connector switch option (522 & 522C)
- Tri‑colour (3‑colour) dial option for filter status (522C & 555A)
- Compact, suitable for outdoor and “hose‑down” installations (522)
- 5 year warranty (522); 1 year warranty (522C & 555A)
- Simple installation, ¼” FNPT end connections (all models)
Mid‑West Instrument 522 family provides compact, competitively priced differential pressure indicators and gauge/switches for filter monitoring and other DP applications. All models are rugged and suited to many plant and field installations, reverse pressure should be avoided on the rolling‑diaphragm units.
DP Range And Accuracy
Model 522 / 522C: 0–5 PSID (0–34.5 kPa) thru 0–50 PSID (0–344.7 kPa)
Model 555A: 0–3.5 PSID (0–24.1 kPa) thru 0–43 PSID (0–296.5 kPa)
Differential Full Scale Ascending Accuracy: ±5% (ASME B40.1 Grade D)
Notes on DP sensing and use: Rolling diaphragm and diaphragm type indicators are designed primarily for gas and low differential liquid applications. Reverse pressure should be avoided on rolling diaphragm models. For filter monitoring use the tri‑colour dial versions (522C or 555A) for rapid visual identification of Clean / Change / Dirty condition.
Model 555A: 0–3.5 PSID (0–24.1 kPa) thru 0–43 PSID (0–296.5 kPa)
Differential Full Scale Ascending Accuracy: ±5% (ASME B40.1 Grade D)
Notes on DP sensing and use: Rolling diaphragm and diaphragm type indicators are designed primarily for gas and low differential liquid applications. Reverse pressure should be avoided on rolling diaphragm models. For filter monitoring use the tri‑colour dial versions (522C or 555A) for rapid visual identification of Clean / Change / Dirty condition.
Model 522 4.5 Inch Dial
Model 522A
Common Options
Available dial sizes
Model 522: 2½” and 4½” diameter
Model 522C: 2½” diameter
Model 555A: 2½” diameter (two‑sided dial indication)
Dial scale ranges (original format and SI conversion)
Model 522 / 522C: 0–5 PSID (0–34.5 kPa) to 0–50 PSID (0–344.7 kPa)
Model 555A: 0–3.5 PSID (0–24.1 kPa) to 0–43 PSID (0–296.5 kPa)
Differential full scale ascending accuracy: ±5% (ASME B40.1 Grade D)
Working pressures
Model 522 / 522C: 1000 PSIG (6,895 kPa)
Model 555A: 300 PSIG (2,070 kPa)
Operating temperature
Model 522 / 522C: -40°F to +200°F (-40°C to +93°C)
Model 555A: -40°F to +150°F (-40°C to +65.6°C)
Weather protection: Model 522 / 522C: NEMA 4X (specific configurations)
Material of construction body (wetted part)
Model 522 / 522C: Aluminium, Acetal plastic, 316/316L stainless steel (model dependent). Model 555A: Glass filled nylon (GFN) (wetted part).
Internal wetted parts
316 stainless steel, ceramic magnet (as applicable)
Connections
¼” FNPT end connections only
Maximum over‑range protection (High over Low)
200 PSID (1,379 kPa / 14 bar)
Model 522 / 522C (avoid reverse pressure)
Elastomers (O‑rings and diaphragm materials)
Buna‑N and Viton
Model 522: 2½” and 4½” diameter
Model 522C: 2½” diameter
Model 555A: 2½” diameter (two‑sided dial indication)
Dial scale ranges (original format and SI conversion)
Model 522 / 522C: 0–5 PSID (0–34.5 kPa) to 0–50 PSID (0–344.7 kPa)
Model 555A: 0–3.5 PSID (0–24.1 kPa) to 0–43 PSID (0–296.5 kPa)
Differential full scale ascending accuracy: ±5% (ASME B40.1 Grade D)
Working pressures
Model 522 / 522C: 1000 PSIG (6,895 kPa)
Model 555A: 300 PSIG (2,070 kPa)
Operating temperature
Model 522 / 522C: -40°F to +200°F (-40°C to +93°C)
Model 555A: -40°F to +150°F (-40°C to +65.6°C)
Weather protection: Model 522 / 522C: NEMA 4X (specific configurations)
Material of construction body (wetted part)
Model 522 / 522C: Aluminium, Acetal plastic, 316/316L stainless steel (model dependent). Model 555A: Glass filled nylon (GFN) (wetted part).
Internal wetted parts
316 stainless steel, ceramic magnet (as applicable)
Connections
¼” FNPT end connections only
Maximum over‑range protection (High over Low)
200 PSID (1,379 kPa / 14 bar)
Model 522 / 522C (avoid reverse pressure)
Elastomers (O‑rings and diaphragm materials)
Buna‑N and Viton
Electrical Configuration
Mid‑West Instrument switches are mechanically adjustable allowing customer to set the switch within a defined adjustment span of the instrument. Mid‑West can pre‑set switch set point(s) on request. All non‑hazardous switches are CE marked per EU Low Voltage & RoHS Directives.
Switches are optional. No power required to operate mechanical switches.
Available enclosures: flat pack case with jacketed flying leads or DIN IP65 / NEMA 4X plug‑in connector. DIN compression plug accepts and seals on 4.5–7 mm cable.
Switch location: top only.
CE marked for compliance with Low Voltage (double insulation) & RoHS Directives.
Common Applications
Filter and strainer monitoring
Compressed air systems
Hydraulic systems (where pressure ratings permit)
Refrigerant systems (model dependent)
Pump performance testing
Heat exchanger differential monitoring
Water treatment systems
Switches are optional. No power required to operate mechanical switches.
Available enclosures: flat pack case with jacketed flying leads or DIN IP65 / NEMA 4X plug‑in connector. DIN compression plug accepts and seals on 4.5–7 mm cable.
Switch location: top only.
CE marked for compliance with Low Voltage (double insulation) & RoHS Directives.
Common Applications
Filter and strainer monitoring
Compressed air systems
Hydraulic systems (where pressure ratings permit)
Refrigerant systems (model dependent)
Pump performance testing
Heat exchanger differential monitoring
Water treatment systems
Model 522C
Additional Services
Custom Dial Face
Personalised dial faces tailored to your specifications.
Tagging Service
Services include stainless steel tags with wire or screw options.
Calibration Report
Calibration and accuracy certification from Mid-West or CMC.
Modification Service
Modification of existing stock units to for specific dial and electrical requirements.