Series DH3 Digihelic® Differential Pressure Controller

Digihelic® Controller in Photohelic® Gage, Square Root Output for Flow

The Series DH3 Digihelic® Differential Pressure Controller is a 3 in 1 instrument possessing a digital display gage, control relay switches, and a transmitter with current output all packed in the popular Photohelic® gage style housing. Combining these 3 features allows the reduction of several instruments with one product, saving inventory, installation time and money. The Digihelic® controller is the ideal instrument for pressure, velocity and flow applications, achieving a 1% full scale accuracy on ranges down to the extremely low 0.25" w.c. to 2.5" w.c. full scale. Ranges of 5" w.c. and greater maintain 0.5% F.S. accuracy. Bi-directional ranges are also available.

The Series DH3 Digihelic® controller allows the selection of pressure, velocity or volumetric flow operation in several commonly used engineering units. 2 SPDT control relays with adjustable deadbands are provided along with a scalable 4-20 mA process output.

Programming is easy using the menu key to access 5 simplified menus which provide access to: security level; selection of pressure, velocity or flow operation; selection of engineering units; K-factor for use with flow sensors; rectangular or circular duct for inputting area in flow applications; set point control or set point and alarm operation; alarm operation as a high, low or high/low alarm; automatic or manual alarm reset; alarm delay; view peak and valley process reading; digital damping for smoothing erratic process applications; scaling the 4-20 mA process output to fit your applications range and field calibration.

Please see SERIES AT2DH3 for ATEX approved.

Product Applications

  • SCFM flow in ducts
  • Filter status
  • Static pressures in ducts or buildings
  • Damper control
  • Fan control

Models & Ordering

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Model Number Description Usually Ships Price Order
DH3-002 Differential Pressure Controller, range 0-0.25" w.c. Same Day $355.00 Order
DH3-003 Differential Pressure Controller, range 0-0.5" w.c. Same Day $289.00 Order
DH3-004 Differential Pressure Controller, range 0-1" w.c. Same Day $289.00 Order
DH3-005 Differential Pressure Controller, range 0-2.5" w.c. Same Day $289.00 Order
DH3-006 Differential Pressure Controller, range 0-5" w.c. Same Day $289.00 Order
DH3-007 Differential Pressure Controller, range 0-10" w.c. Same Day $289.00 Order
DH3-009 Differential Pressure Controller, range 0-25" w.c. Same Day $289.00 Order
DH3-010 Differential Pressure Controller, range 0-50" w.c. Same Day $289.00 Order
DH3-011 Differential Pressure Controller, range 0-100" w.c. Same Day $289.00 Order

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Air and non-combustible, compatible gases.
Wetted Materials:
Consult factory.
Housing Material:
Die cast aluminum case and bezel.
±1.5% for 0.25" and ±0.25" w.c. ranges. Ranges 0.5" to 5" w.c. and corresponding bi-directional (except ±2.5" w.c.) ±1%; All other ranges: ±0.5% @ 77°F (25°C) including hysteresis and repeatability (after 1 hour warm-up).
< ±1% per year.
Pressure Limits:
Ranges ≤ 2.5 in w.c.: 25 psi; ±2.5", 5 in w.c.: 5 psi; 10 in w.c.: 5 psi; 25 in w.c.: 5 psi; 50 in w.c.: 5 psi; 100 in w.c.: 9 psi.
Temperature Limits:
32 to 140°F (0 to 60°C).
Compensated Temperature Limits:
32 to 140°F (0 to 60°C).
Thermal Effects:
0.020%/°F (0.036/°C) from 77°F (25°C). For 0.25" and ±0.25" w.c. ranges: ±0.03%/°F (±0.054%/°C).
Power Requirements:
12-28 VDC, 12-28 VAC 50 to 400 Hz.
Power Consumption:
3 VA max.
Output Signal:
4-20 mA DC into 900 ohms max.
Zero & Span Adjustments:
Accessible via menus.
Response Time:
250 ms (damping set to 1).
Backlit 4 digit LCD 0.4" height LED indicators for set point and alarm status.
Electrical Connections:
15 pin male high density D-sub connection. 18" (46 cm) cable with 10 conductors included. 4' and 10' cables available.
Process Connections:
1/8" female NPT. Side or back connections.
Mounting Orientation:
Mount unit in vertical plane.
5" (127 mm) OD x 3-1/8" (79.38 mm).
1.75 lb (794 g).
Agency Approvals:

Switch Type:
2 SPDT relays.
Electrical Rating:
1 amp @ 30 VAC/VDC.
Set Point Adjustment:
Adjustable via keypad on face.


Model Number Description Usually Ships Price Code Order
A-298 Flat aluminum bracket for flush mounting Photohelic® & Capsuhelic® gages, 603A, 605, and 3000MR. Same Day $27.75 Order
A-301 Static pressure tip, for 1/4" metal tubing connection. Same Day $9.90 Order
A-302 Static pressure tip, for 3/16" and 1/8" ID plastic or rubber tubing. Same Day $9.10 Order
A-302F-A 303SS static pressure tip with mounting flange, 4" hook style. For 3/16" ID rubber or plastic tubing, includes mounting screws. Same Day $9.10 Order
A-370 Flush mount bracket used with: Photohelic® 3000MR/MRS, Capsuhelic®, 631B Transmitter, EDA. Bracket is then surface mounted. Steel with gray hammertone epoxy finish. Same Day $33.75 Order
A-489 4" 303 SS straight static pressure tip with flange. Same Day $6.67 Order
A-700 Power supply ( 0.5 A). Same Day $84.00 B Order


Model Chart

EXAMPLE DH3 002 AT Series DH3-002-AT Digihelic® Differential Pressure Controller, range 0.25" w.c., with aluminum tag.
SERIES DH3     Digihelic® Differential Pressure Controller
RANGE   002
  0.25" w.c.
0.5" w.c.
1" w.c.
2.5" w.c.
5" w.c.
10" w.c.
25" w.c.
50" w.c.
100" w.c.
0.25-0-0.25" w.c.
0.5-0-0.5" w.c.
1-0-1" w.c.
2.5-0-2.5" w.c.
5-0-5" w.c.
10-0-10" w.c.
Aluminum Tag
Certificate of Origin
NIST Certificate of Calibration
Stainless Steel Tag

Product Literature


Catalog Pages




A customer would like to get switching capability, local pressure indication, and a 4-20 mA output signal all in one device. Do we have a product to offer them?
Yes. The DH, DHII or DH3 possess high/low set points, digital gage display and 4-20 mA full scale output signal for air and compatible gas. The EDA, DPG-200, DPT and the MDPC possess high/low set points, digital gage display and 4-20 mA full scale output signal for compatible fluids.
Your Magnehelic gauge doesn't come with a calibration certificate, do you have any documentation for these gauges to meet these needs?
We have 3 options: (1) We can supply a Certificate of Conformance at no charge if you request that certificate at the time of order. The Certificate of conformance would state that each Magnehelic gauge is calibrated to meet the specifications stated on the spec sheet. (2) We offer a factory calibration “-FC” as an option that is a certificate of the standard calibration points at the time of manufacture, for a small fee. (3) We can also provide a NIST-traceable calibration for an extra charge per gage if that is required. To get the NIST-traceable calibration, you would simply add a “-NIST” to the end of your part number. NIST-traceable calibrations will come with the 6 point calibration certificate. We recommend “periodic calibration” for our Magnehelic, though we leave the specific time-frame up to the end user, since different organizations have different requirements (i.e. government groups often require more frequent calibrations.) If you choose to have the NIST traceable calibration done, the NIST group (the National Institute of Standards and Technology) dictates yearly calibration and it will be printed on the certificate.
I am using DH3 Digihelic differential pressure controllers for my applications. The instruction says that "the Alarm can be reset by the RESET key on the front panel, or an external reset switch". For the second case (reset by external reset switch), could you let me know how to do it? The instruction doesn't provide any related detail. Thanks in advance.
Unfortunately, contrary to what was printed in the instruction manual, the DH3 does not have the ability for the alarm to be reset via an external reset switch, mainly due to the limited number of pins available in the electrical connector. This feature is only available in the DH and DHII series Digihelics.

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