Dwyer MP User Manual

Series MP Mini-Photohelic

®

Differential Pressure Switch/Gage

Specifications - Installation and Operating Instructions

Bulletin B-37-A

LOW PRESSURE

PORT

HIGH PRESSURE

PORT

3-1/32 [77.00]

1 [25.4]

Ø2-19/32

%%3-1/16

[77.79]

[65.88]

3-1/32 [77.00]

3-13/16 [96.84]

23/64 [36.51]

SPECIFICATIONS

GAGE SPECIFICATIONS
Service: Air and non-combustible, compatible gases.
Wetted Materials: Consult factory.
Accuracy: +/- 5% of full scale @ 70°F (21.1°C). Gage

face mounted in vertical position.

Pressure Limits: 30 psig (2.067 bar).
Temperature Limits: 20 to 120ºF (-6.7 to 49°C).
Process Connections: Barbed for 3/16˝ I.D. tubing

(STD); 1/8˝ male NPT (optional).
Size: 4-1/8˝ (104.78 mm) depth x 3-1/16˝ (77.79 mm)
diameter.

Weight: 23 oz (652 g).

The Series MP Mini-Photohelic®differential pres-

sure switch/gage combines the time proven
Minihelic
SPDT switching setpoints. The Mini-Photohelic

®

II differential pressure gage with two

®

is
designed to measure and control positive, negative,
or differential pressures consisting of non-com­bustible and non-corrosive gases. Gage reading is
independent of switch operation. Switching status is
visible by LED indicators located on the front and
rear of the gage.

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

SWITCH SPECIFICATIONS
Switch Type: (2) SPDT relays.
Electrical Rating: 5A @ 120/240 VAC Resistive; 5A @

30 VDC.
Electrical Connections: Screw Type Terminal Block.
Accepts 22-12 AWG wire.
Power Requirements: 24 VDC / 24 VAC 50/60 Hz 4
watts.

Mounting Orientation: Gage face in vertical position.
Set Point Adjustment: Push Buttons.
Standard Accessories: (2) mounting screws, (1) .050˝

hex allen wrench.

Agency Approvals: UL, cUL.

Phone: [phone] www.dwyer-inst.com

INSTALLATION

PANEL MOUNTED

#6 MOUNTING

SCREW

MOUNTING
LUG

1. Location: Select a location free from excessive

vibration and where ambient temperature will be
between 20 to 120ºF (-6.7 to 49ºC). Pressure sensing
lines may be any length necessary without affecting
accuracy. However, long runs of tubing will dampen
readings slightly and cause an increase in response
time. If pulsing pressure or vibration cause excessive
pointer oscillation please contact factory for ways to pro­vide additional damping.

4. Zeroing: Before installation, the Mini-Photohelic®may

need to be zeroed before placing into operation. If
zeroing is required, you must first remove the zero
adjust plug, located near the bottom face of the gage,
with a small blade screwdriver. (refer to Fig B.) The
zero adjust screw is located directly behind the plug.
Use the hex allen wrench supplied and adjust until the
pointer is on zero. This must be done with both pres­sure connections vented to the atmosphere and the
gage oriented in the final mounting position. Replace
plug. Caution must be taken not to overtighten the
plastic plug when repluging.

2. Position: The Mini-Photohelic®is calibrated and zeroed

with gage face in the vertical position at the factory. If the
gage is used in any other position, it must be re-zeroed
each time the position is changed. Gages with ranges
under 5 in. w.c. (1.24 kPa), or equivalent, should be
used only in the vertical position unless special calibra­tion was specified when ordering.

3. Mounting: The Mini-Photohelic®is normally mounted

before making electrical connections. Terminal blocks
are located on the rear of the gage for electrical connec­tions.

(A) Panel Mounting: Standard installation for the Mini-

Photohelic®mounting is flush through a panel.
Allow approximately 1˝ clearance for pressure tub­ing and electrical wiring. cut a 2-5/8˝ (66.68 mm)
diameter hole in the panel. Insert the Mini­Photohelic®into the panel, thread #6 mounting
screws into the mounting lugs and tighten.

Fig. A

LOW PRESSURE PORT

2-19/32
(65.88)

3-1/16

1 (25.40)

(77.79)

5. Pneumatic Connections: To measure positive pres-

sure, connect tubing to port marked “+” and vent “–”
port to atmosphere. For negative pressure (vacuum),
connect to port marked “–” and vent “+” port to atmos­phere. If gage is supplied with 1/8˝ male NPT connec­tions careful attention must be made not to over-tight­en fittings to avoid damage to the gage.

HIGH PRESSURE PORT

ZERO ADJUST PLUG

5/32 (3.97)

MOUNTING HOLE

TYP 4 PLACES

2.276 (57.81) TYP

2-11/16 (68.26) SQ

Fig. B

2-3/8

(60.33)

1-15/16
(49.21)

1-7/16

(36.51)

11/64
(4.37)

23/64
(9.13)