Dwyer 655A User Manual

Bulletin P-4-655A

655A-XX-P MODELS

(4-3/4) [120.65]

2 [50.80]

4 WIRE CABLE

1/4” FEMALE NPT

1-1/4 [31.75]

Series 655A Wet/Wet Differential Pressure Transmitter

Specifications - Installation and Operating Instructions

The Series 655A Differential Pressure Transmitter converts a positive

differential pressure measurement into a standard 4-20 mA output
signal. Designed for use as a wet/wet differential pressure transmitter, it
can be used to measure gas or liquid pressure compatible with 316L
stainless steel wetted parts. With an accuracy of < ±0.25% (BFSL, RSS),
the Series 655A Pressure Transmitter can measure low differential
pressures, but can withstand working pressures to a maximum of 1000
psi (68.95 bar), 3000 psi (206.8 bar) burst.

INSTALLATION

Location

Select a location where the temperature of the transmitter will be
between -20 to 200°F (-29 to 93°C). Distance from the receiver is limited
only by total loop resistance. Tubing or piping of extended lengths will
increase response time slightly.

Position

The transmitter is not position sensitive. However, all standard models
are originally calibrated with the unit in a vertical position and with the
pressure connections at horizontal. Although they can be used at other
angles, for best accuracy it is recommended that zeroing and spanning
be done while unit is in the alternative position.

Pressure Connections

Pressure connections are 1/4˝ female NPT. Use a small amount of
plumbers thread tape or other suitable sealant to prevent leaks. Be sure
the pressure passage inside the port is not blocked.

SPECIFICATIONS
Service: Compatible gasses or liquids.
Wetted Materials: 316L SST.
Accuracy: ±0.25% BFSL, RSS (combined effect of non-linearity,

hysteresis, and repeatability).

Stability: ≤ ±0.25% FSO/yr.
Temperature Limits: -20 to 200°F (-29 to 93°C).
Compensated Temperature Limits: 0 to 170°F (-17.8 to 76.7°C).
Pressure Limits: 1000 psi (68.95 bar) continuous; 3000 psi (206.8

bar) burst.

Thermal Effects: ≤ ±1.5% F.S. oven comp. temperature range.
Power Requirements: 8 to 38 Vdc.
Output Signal: 4 to 20 mA.
Static Pressure Effects: on zero: ≤ ±0.25% FSO per 1000 psi;

on span: ≤ ±0.5% of reading per 1000 psi.

Loop Resistance: 1500 ohms.
Electrical Connections: Cable exit with 24˝ cable; optional 6-pin

connector.

Process Connections: 1/4˝ NPT female.
Enclosure Rating: Designed to meet NEMA 4X (IP66).
Mounting Orientation: Mount in vertical position: zero shifts up to

1˝ ±H2O depending on orientation.

Response Time: < 10 mS.
Weight: 18 oz (510 g).
Agency Approval: CE.

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]

Electrical Connections

A-232 CONNECTOR END

OPPOSITE END IS SIX WIRES

COLORS: RED POSITIVE,

BLACK NEGATIVE,

GREEN CASE GROUND

PRESSURE
TRANSMITTER

POWER
SUPPLY
8-38 VDC

RED WIRE

BLACK WIRE

RECEIVER

1400

1500
1300

1200
1100
1000

900
800
700
600
500
400
300

200
100

05

10

15

20

25 30

35

40

VDC

R MAX= Vps-8.0

20 mA DC

L

RECEIVER RESISTANCE (Ω)

Operating

Range

Use A-232 with 6˝ pin connection models

Wire Length

The maximum length of wire connecting the transmitter and receiver is
a function of wire size and receiver resistance. Wiring should not
contribute more than 10% of the receiver resistance to total loop
resistance. For extremely long runs (over 1000 feet (305 m)), choose
receivers with lower resistance to minimize the size and cost of
connecting leads. Where wiring length is under 100 feet (30.5 m), wire
as small as 22 AWG can be used.

Two (2)-Wire Operation

An external power supply delivering 8 to 38 Vdc with minimum current
capability of 40 mA DC (per transmitter) is required to power the control
loop. The range of appropriate receiver load resistance for the DC power
supply voltage available is expressed by the formula and graph below.
Shielded two wire cable is recommended for control loop wiring.

2-WIRE CONNECTION

POWER SUPPLY VOLTAGE - VDC

MAINTENANCE

Upon final installation of the Series 655A Differential Pressure
Transmitter, no routine maintenance is required. A periodic check of
system calibration is recommended. The Series 655A 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. 2/09 FR# R1-443718-00

DWYER INSTRUMENTS, INC.

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

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