1. Home
  2. Laminar Flow Hoods, Fume Hoods, Biosafety Cabinets
  3. Hood Accessories
  4. Magnehelic® Gauges

Differential Pressure Gauges/Controller

Differential Pressure Gauges/Controller Differential Pressure Gauges/Controller
Differential Pressure Gauges/Controller Differential Pressure Gauges/Controller
  • Measure and control both positive and negative low air or gas pressures
  • Provide an ideal way of monitoring and controlling the positive pressure differential required for cleanrooms
  • Enable you to meet FED STD 209E regarding cleanroom pressure
  • Ideal for measuring differential pressure in gloveboxes and air flow in exhaust hoods
  • MAGNEHELIC® Principle ensures wear-free accuracy within 2% of full scale
  • Resists shock and vibration
  • Available in a number of pressure gauges to suit a wide range of applications, such as gauging air filters, monitoring air conditioning systems, and measuring static air pressure and air vehicles

If your facility incorporates a laminar flow cleanroom, these MAGNEHELIC® and PHOTOHELIC® differential pressure gauges can help you maintain the positive pressure necessary to block inrushing contaminants that can damage sensitive materials and operations. In doing so, they also help to meet the requirements and recommendations set forth in FED STD 209E which specifies that a minimum positive pressure of 0.05" (1 mm) of water differential be maintained between the cleanroom and adjacent areas.

Chatterless, Wear-Free Accuracy
These gauges incorporate an exclusive MAGNEHELIC® Principle that eliminates wear, backlash, and hysteresis. The result is a remarkably high standard of accurate, dependable gauge performance at a modest price.

This MAGNEHELIC® Principle is a method of transmitting the effects of changes in air pressure from a diaphragm to an indicating pointer—by means of magnetic linkage and without the use of gears or other direct mechanical linkages. This system avoids wear and physical contact, which might destroy the accuracy and sensitivity of the instrument. It delivers accuracy to within 2% of full scale.

This principle offers numerous advantages over other gauges. Because it uses no fluid, it eliminates evaporation, freezing, or toxicity problems. It also ensures inertia-free, drift-free pointer movement and offers unusually high resistance to shock and vibration. These gauges are also unharmed by pressure surges up to 15 psig and by ambient temperature fluctuations between 20 and 140 degrees F (-7 and 60°C) .

Both MAGNEHELIC® and PHOTOHELIC® gauges feature easy-to-read 4" (102 mm) dials that quickly provide gas pressures—positive, negative or differential. Because operation does not depend on gravity, you can either face- or flush-mount them in any position. Gauges can also be mounted on panels either inside or outside of the cleanroom; if mounted inside, the low pressure ports of the room pressure gauges can be connected together, and a single tube routed to outside the room.

Versatile Applications
Use the MAGNEHELIC® gauges (range of .25-4.0" WC) to determine positive pressure differentials between the cleanroom and adjacent areas. MAGNEHELIC® gauges can also be used to measure pressure drops across pre-filters and absolute filters.

A PHOTOHELIC® gauge/switch can also be used to control makeup or exhaust air dampers in order to maintain the room pressure within prescribed limits. All gauges can be mounted on a control panel. Gauge calibration is accomplished between room readings. In this application the PHOTOHELIC® gauge serves as the “master” gauge.

These units can also be used to check air filters, to sense static pressure or to measure air velocity and volume.

The MAGNEHELIC<sup>®</sup> Pressure Gauge

The MAGNEHELIC® Pressure Gauge

The Magnehelic® is the industry standard to measure fan and blowerpressures, filter resistance, air velocity, furnace draft, pressure drop across orifice plates, liquid levels with bubbler systems and pressures in fluid am-plifier or fluidic systems. It also checks gas-air ratio controls and automatic valves, and monitors blood and respiratory pressures in medical care equipment.
Pressure Range
(inches WC)
Weight Uninstalled Installed
Dwyer Part # Cat. # Price Dwyer Part # Cat. # Price
0-0.5 1 lb. 2 ozs.
511 g
MARKII 0-3 MODEL 25 2625-08 $ 133 3T315 2625-30 $ 350
0-1.0 1 lb. 2 ozs.
511 g.
2000-0 2625-09 $ 133 2001 2625-31 $ 340
0-2.0 1 lb. 2 ozs.
511 g.
2001 2625-10 $ 116 2002 2625-32 $ 340
0-3.0 1 lb. 2 ozs.
511 g.
2002 2625-11 $ 133 2003 2625-33 $ 340
0-4.0 1 lb. 2 ozs.
511 g.
2003 2625-12 $ 140 2004 2625-34 $ 348
.25-0-.25 1 lb. 2 ozs.
511 g.
2004 2300-0 6600-86 $ 416

PHOTOHELIC<sup>®</sup> Pressure Control

PHOTOHELIC® Pressure Control

PHOTOHELIC® models combine the MAGNEHELIC® gauge with a precise pressure switch that lets you control low and high gas pressures. Knob controls adjust dual set points, which allow for variable deadband control. These set points contain photocells that actuate DPDT relays when room pressures reach a preset upper or lower limit, and they can be set up to control corrective damper action. As the room pressure changes in response to damper motion, and the indicator returns to the null band, damper motion is halted.
Pressure Range
(inches WC)
Weight Uninstalled Installed
Dwyer Part # Cat. # Price Dwyer Part # Cat. # Price
0-0.5 4 lbs.
1814 g.
A3000-0 2625-13 $ 311 A3000-0 2625-35 $ 635
0-1.0 4 lbs.
1814 g.
A3001 2625-14 $ 371 A3001 2625-36 $ 635
0-2.0 4 lbs.
1814 g.
A3002 2625-15 $ 358 A3002 2625-37 $ 635
0-3.0 4 lbs.
1814 g.
A3003 2625-16 $ 421 A3003 2625-38 $ 635
0-4.0 4 lbs.
1814 g.
A3004 2625-17 $ 416 A3004 2625-39 $ 635
.25-0-.25 4 lbs.
1814 g
  A3300-0 6600-87 $ 664

Minihelic II<sup>®</sup> Differential Pressure Gauges

Minihelic II® Differential Pressure Gauges

Combining clean design, small size and low cost with enough accuracy for all but the most demanding applications our Minihelic®II gauge offers the latest in design features for a dial type differential pressure gauge. It is our most compact gauge but is easy to read and can safely operate at total pressures up to 30 psig. The Minihelic®II is designed for panel mounting in a single 25⁄8" (79 mm) diameter hole. Standard pressure connections are barbed fittings for .1875" (5 mm) I.D. tubing; optional .125" male NPT connections are also available. Over-pressure protection is built into the Minihelic II® gauge by means of a blow-out membrane molded in conjunction with the diaphragm. Accidental over-ranging up to the rated total pressure will not damage the gauge.

With removable lens and rear housing, the gauge may be easily serviced at minimum cost. With the housing molded from mineral and glass-filled nylon and the lens molded from polycarbonate, the gauge will with stand rough use and exposure as well as high total pressure. The 5% accuracy and low cost of the Minihelic®II gauge make it well suited for a wide variety of OEM and user applications.

Pressure Range
(inches WC)
Weight Uninstalled Installed
Dwyer Part # Cat. # Price Dwyer Part # Cat. # Price
0-0.5 6 ozs.
170 g
2-5000-0 2625-43 $ 128 2-5000-0 2625-48 $ 240
0-1.0 6 ozs.
170 g
2-5001 2625-44 $ 110 2-5001 2625-49 $ 217
0-2.0 6 ozs.
170 g
2-5002 2625-45 $ 87 2-5002 2625-50 $ 217
0-3.0 6 ozs.
170 g
2-5003 2625-46 $ 87 2-5003 2625-51 $ 240
0-5.0 6 ozs.
170 g
2-5005 2625-47 $ 87 2-5005 2625-52 $ 217

DIGIHELIC<sup>®</sup> Differential Pressure Gauge

DIGIHELIC® Differential Pressure Gauge

The Digihelic® differential pressure controller is a 3-in-1 instrument possessing a digital display gauge, control relay switches, and a transmitter with current output. Combining these three features is a cost efficient way to save on the number of instruments needed to measure pressure, velocity and flow. The Digihelic® can achieve a 0.5% full scale accuracy, making it the perfect controller for glove boxes, hoods and clean rooms.

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

The Digihelic® allows you to require a security code prior to any changes to the user-set programming. An easy to use, menu driven keypad also lets you set all of the following: pressure, velocity or flow operation; 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; high/low alarm; automatic or manual alarm reset; alarm delay; view peak and valley process readings; digital dampening for smoothing erratic process applications; Modbus® communications; and field calibration.

DIGIHELIC® Differential Pressure Gauge
Pressure Range
(inches WC)
Weight Uninstalled Installed
Dwyer Part # Cat. # Price** Dwyer Part # Cat. # Price**
0 – 1.0 14 lbs.
6350 g.
DH-004 2625-26 $ 542 DH-004 2625-40 $ 936
0 – 5.0 14 lbs.
6350 g.
DH-006 2625-27 $ 426 DH-006 2625-41 $ 772
1.0 – 0 – 1.0* 14 lbs.
6350 g.
DH-014 2625-28 $ 542 DH-014 2625-42 $ 995
*Bi-Direction Range. Velocity and volumetric flow not available on bi-directional unit.
**Price includes installation
Click to leave a message. 24-hour sales and tech phone support, M - F
Call a Terra Hood specialist direct
Hours: 5:30 - 17:30 M-F
(your local time)
Go to...
Go To