These Barton Instruments DP Indicating Switches are responsive to relatively low magnitudes of pressure differences at high static pressures. They are offered in a wide range of DP ratings and can withstand over-ranges equal to their rated SWP. Typically they are used to energize alarm or control circuits.

• Stable calibration and negligible SP shift
• Minimal Maintenance
• Available in stainless steel (M289AS)


M199-based 289A and 291B are used where maximum sensitivity is required in lower DP ranges, where a field change is anticipated, or when a built-in pulsation dampener is needed
to control the unit’s response time. The 289C is also available in stainless Steel (289AS).
M224C-based 288C and 290D are used in applications that require extended DP ranges (beyond M199-based units) or whenever size and weight are prime considerations.
The 288C is also available in stainless steel (288CS).

The indicating pointer travels through a 270° arc over a six-inch (150mm) dial. Scales are calibrated in uniform increments for measurement of DP or liquid level; square root available for direct reading of flow rate; also special scales for tank fluid quantity.

Weather-Proof Case
The weather-proof case is made of die-cast aluminum, finished with weather-resistant black epoxy resin paint. The polycarbonate lens is secured in the bezel with elastomer ring, reducing possibility of breakage and acts as a seal between bezel and case for a moisture-, fume-, and dustfree atmosphere for the indicating mechanism.

Explosion-Proof Case
NEMA 4 case has a large cover for maximum readability; switches/adj accessible with cover removed. Case is certified for Class I, Div. 1, Group B Explosion-proof service.

Indicating Mechanism
A precision made, jeweled, rotary movement employs a thermally stable Ni-Span-C hair spring. Zero/range adj. via micrometer screws. Zero adj. accessible without removing
scaleplate or pointer. The rotary movement/pointer are fully protected from over-range in either direction.

All models are available in single or dual snap-acting mechanical contact (SPDT) switch configurations. They can be set for high or low, or both when two contacts are furnished. The
switches are adjustable from 5% to 95% of full scale range. Switch set points are adjusted with a control screw located flush with the scale; contact setting indicated by a small scale on scaleplate. Switch contacts can be set to either open or close with increasing or decreasing DP (reverse action by reversing lead wires at terminal block).

AC Rating:
5 amps 125V
2.5 amps 126V-250V

DC Rating:
(Inductive) 1.0 amps 30V
(Resistive) 3.0 amps 30V

Switch connections are 1/2″ NPT Female or an optional flexible conduit (up to 8 feet in length).

Extra product images

Barton Instruments Models 288C / 289A / 290D / 291B Barton Instruments Explosion Proof Case


Controls Flow Valves Gas Oil Repair Maintenance Combustion Actuators Burner Overhaul Contact