Dwyer 681 User Manual
Page 2
2
3
Venting - The 681 is vented to atmosphere through the cable to achieve best accuracy.
This is particularly important for models with pressure ranges below 30 psig. Connections
to the cable should be made in a junction box that is vented to atmosphere, with care taken
to insure that the end of the cable is not blocked or sealed.
Junction Box Suggestion - The following junction box configuration is a recommended
method of terminating the 681’s signal cable in order to achieve a moisture resistant and
vented connection.
Junction Box
Cable Strain Relief
Part No.
A-533PC1
3237 Heyco Flex Fitting
Dimensions:
4.92" x 2.95" x 2.95"
2.50" Long
Manufacturer:
Hoffman Engineering Co.
Heyco
900 Ehlen Drive
Kenilworth, NJ 07033
Anoka, MN 55303
(201) 245-0033
(612) 421-2240
(800) 526-4182
1.
Drill one 1/2" dia. hole at each end of junction box for cable strain reliefs. Note: if
conduit is to be installed, omit one 1/2" hole and drill appropriate hole for conduit.
2.
Drill and tap one 1/2"–13 NC hole in bottom of junction box and install loosely one 1/2"-
13 NC plastic or stainless steel screw. The clearance between threads serves as a
vent for the box.
3.
Install cable strain reliefs in 1/2" dia. holes. If using conduit at one end, be sure it is
sealed properly against moisture.
4.
Mount junction box and install cables.
Electrical Connections - The Sereis 681 (current output) Sanitary Transmitter is a true 2-
wire, 4-20 mA current output device and delivers rated current to any external load of 0-800
ohms. The 681 has a two wire cable where red is positive and black is negative.
S
Z
C-290
Vent Screw
Junction Box
Strain Relief
1/2" Conduit Fitting
1/2" Conduit optionally
The 4-20mA current output circuit is designed to have current flow in one direction only
please observe polarity. It is suggested that the cable shield be connected to the system
loop circuit ground to improve electrical noise rejection.
CALIBRATION
All Dwyer pressure transmitters are carefully calibrated to the specific input pressure range
vs. output current at the factory so little or no field calibrating is necessary. Series 681
transmitters (4-20 mA) are factory calibrated using a 250 ohm load at 24 VDC. External
zero and span adjustment capability is approximately
±
0.5 mA, individually. Zero and span
adjustments are made by removing the pan head screws and turning the potentiometer
screw inside. A jeweler’s screwdriver or a .015" x 3/32" flathead screwdriver with a 3" shaft
is easiest to use for making zero and span adjustments. It is important to replace the screws
after adjustments are made to avoid allowing moisture to enter the transmitter.
RETURNING PRODUCTS FOR REPAIR
Please contact Dwyer (800-872-9149 or 219-879-8868) to review information relative to your
application before returning unit for repair 2. Many times only minor field ajustments may
be necessary. When returning a product to Dwyer Instruments, the material should be
carefully packaged and shipped prepaid to:
Dwyer Instruments
Attn: Repair Department
102 Indiana Highway 212
Michigan City, IN 46360
To assure prompt handling, please supply the following information and include it inside the
package of returned material:
1.
Name and phone number of person to contact.
2.
Shipping and billing instructions
3.
Full description of the malfunction.
4.
Identify any hazardous material used with product.
Notes: Please remove any pressure fittings and plumbing that you have installed and
enclose any required mating electrical connectors and wiring diagrams.
Allow approximately 3 weeks after receipt at Dwyer for the repair and return of the unit.
Non-warranty repairs will not be made without customer approval and a purchase order to
cover repair charges.
Calibration Services
Dwyer maintains a complete calibration facility that is traceable to the National Institute of
Standards & Technology (NIST). If you would like to recalibrate or recertify your Dwyer
pressure transducers or transmitters, please call our Repair Department at 1-800-872-9141
or 219-879-8868 for scheduling, cost and turn around estimates.
Setra
Transmitter
(4-20 mA)
Power Supply
Load
(Monitor)
-
+
+
+
-
-