Dwyer Instruments MP-003, MP-25MM, MP-000, MP-002, MP-10PSI 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]

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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

MOUNTING HOLE

5/32 (3.97)

TYP 4 PLACES

2.276 (57.81) TYP

2-11/16 (68.26) SQ

2-3/8

(60.33)

1-15/16
(49.21)

1-7/16

(36.51)

11/64
(4.37)

23/64
(9.13)

Fig. B

ZERO ADJUST PLUG

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6. Electrical Connections: Refer to Fig. C for electrical

connections located on rear on Mini-Photohelic
Switch/Gage:

S1→SP1 Reset Terminal (Do not apply power)

Sectio

n

S1→SP1 Reset Terminal (Do not apply power)
S2→SP2 Reset Terminal (Do not apply power)
S2→SP2 Reset Terminal (Do not apply power)

Sectio

n

Vs→24 VDC / 24 VAC 50/60 HZ
Vs→24 VDC / 24 VAC 50/60 HZ

NO1

SP1 Relay N.O. Contact

→

C1→SP1 Relay Common Contact

Sectio

n

NC1
NO2

SP1 Relay N.C. Contact

→

SP2 Relay N.O. Contact

→

C2→SP2 Relay Common Contact

NC2

SP2 Relay N.C. Contact

→

Fig. C

®

8. Circuit Style: The Mini-Photohelic®Switch/Gage is

available with several factory installed optional cir­cuits. They are identified by the label shown in Fig. D.
This label is mounted on the upper side of the main
pressure housing.

The letter H denotes a circuit in which the relay can be
made to latch or remain energized after pressure
increases above its setpoint.

The letter L denotes a circuit in which the relay can be
made to latch or remain de-energized after pressure
decreases below its setpoint.

Two letters are required to fully identify a dual setpoint
unit. Thus, circuit style HH, which is standard, is a dual
setpoint circuit which has provisions for latching on
pressure increase to either setpoint. Circuit styles may
be used with either setpoint stated above.

Fig. D

SECTION A

–

SECTION C

SECTION B

+

Section A contains external connections to the holding
circuit for manual reset applications. The function and
use of these connections varies somewhat depending on
the circuit style of the instrument. See steps 7 and 9 for
details.

Caution: Do not apply electrical current to

terminals in Section A.

Section B contains the power connections for the control
unit. Standard unit is designed to operate on 24 VDC / 24
VAC 50/60 HZ.

Caution: Do not apply 120 / 240 VAC to the power

connections.

9. Dual Setpoint Automatic Reset: Circuit style HH is

used for simple on-off switching applications. To place
in service, connect load circuits to the appropriate ter­minals in Section C (Fig. C) for SP1 relay and SP2
relay. No connections are required in Section A.

Section C contains connections for SP1 and SP2 relays.
Connections are marked on the rear of the instrument.

7. Setpoint Calibration: Setpoint calibration is easily

attained by actuating the pushbuttons located on the
rear of the instrument. Pushbuttons are labeled SP1
and SP2. To set the setpoint SP1, apply pressure
where you require the SP1 relay to energize. Press
pushbutton marked SP1 on the rear of the instrument,
SP1 LED located on the front and rear of the instru­ment will flash several times. When LED stops flash­ing calibration is complete. Repeat the same steps
above for SP2 relay.

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10. Dual Setpoint Manual Reset: Circuit style HH may

also be used for manual reset applications where it is
required to maintain contact on either relay following
pressure increase above its setpoint. Load or signal
connections are made to the appropriate terminals in
Section C (as in step 8). Connect terminals in Section
A through normally closed switches or pushbuttons as
shown in Fig. E. Use “dry-circuit” type switches such as
Dwyer Part No. A-601 with palladium, gold, etc. or
rotary wiping action type contacts is recommended.

Fig. E

RESET

NC

24 VDC/VAC

Fig. F

–

LOAD

+

NO

RESET

NC

NO

–

+

Circuit style LL is used for manual reset applications
where it is required to maintain contact on either relay
following pressure decrease below the setpoint. Load
or signal connections are made to the appropriate ter­minals in section C (as in step 8). A normally open type
manual reset switch such as Dwyer Part No. A-601 is
connected to the terminals in Section A. The circuit
must be “armed” by momentarily energizing the switch
while the pointer is to the right of the setpoint. From
that point on, the circuit will latch on pressure decrease
below the setpoint and remain latched on pressure
increase until manually reset with the optional switch.

11. High Low Limit Control - Dual Setpoint: Standard

circuit style HH may be used to control various fans,
dampers, pumps, etc..., between the setpoints of a
Mini-Photohelic® Switch/Gage. To accomplish this, use
one setpoint relay to reset the other as shown in the
wiring diagram Fig. F. In this typical application, the
load would be connected to the N.C. contacts (NC2) of
the right setpoint relay SP2. The N.O. contacts of SP1
relay would be connected to the S2 reset terminals on
the rear of the instrument. On pressure rise to the right
setpoint relay SP2, the relay would pull-in and hold
even though the pressure might fall below that set­point. If the pressure continued to fall to the left of set­point SP1, then SP2 relay would be automatically DE­ENERGIZED, returning to its normal position and in so
doing, open the reset terminal S2. The right setpoint
relay SP2 would thus be reset and the cycle could
repeat.

12. Dual Setpoint Special Purpose Circuits: Circuit

Style LL may be used where manual reset following
maintained contact on pressure decrease to either set­point is required. Circuit HL and LH are combination
units. For special combinations of features and special
units consult factory.

13. Failure Mode: The Mini-Photohelic

®

circuit design pro­vides certain protection in the event of a loss of electri­cal power. Both relays will de-energize upon loss of
power.

MAINTENANCE AND SERVICE

Dwyer Mini-Photohelic®Switch/Gages are precision
instruments, expertly assembled and calibrated at the fac­tory. They require no lubrication or periodic servicing. If
the interior is protected from dust, dirt, corrosive gases
and fluids, years of trouble-free service may be expected.
Zero adjustment should be checked and reset occasional­ly to maintain accuracy.
Upon final installation of the Series MP Mini-Photohelic
Differential Pressure Switch/Gage and the companion
receiver, no routine maintenance is required. A periodic
check of the system calibration is recommended. The
Series MP is not field serviceable and should be returned
if repair is needed (field repair should not be attempted
and may void warranty). Be sure to include a brief descrip­tion of the problem plus any relevant application notes.
Contact customer service to receive a return goods autho­rization number before shipping.

®

©Copyright 2009 Dwyer Instruments, Inc. Printed in U.S.A. 9/09 FR# 14-443249-10 Rev.4

DWYER INSTRUMENTS, INC.

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

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

Find Quality Products Online at: [e-mail]

www.GlobalTestSupply.com