1
1.0 GENERAL INFORMATION
Every Model 856 has been tested and calibrated before shipment. Specific
performance specifications are listed on Page 7 of this Guide.
Gems Sensors 856 pressure transducers sense gauge pressure and convert this
pressure to a proportional high level analog output. Two output versions are
offered: A voltage output of .1 to 5.1 VDC, and a current output of 4 to 20 mA.
2.0 MECHANICAL INSTALLATION
2.1 Media Compatibility
Model 856 transducers are designed to be used with any gas or liquid compat-
ible with 17-4 PH Stainless Steel. (Hydrogen is not recommended for use with
17-4 PH SS.)
2.2 Environment
The operating temperature limits of the 856 are as follows:
Operating Temperature Range
°
F (C
°
)
-40 to +260 (-40 to +125)
Compensated Temperature Range
°
F (C
°
)
-4 to +176 (-20 to +80)
2.3 Pressure Fittings
Typically, standard pipe fittings and installation procedures should be used.
However, for very high pressure ranges in excess of 500 psig, we suggest the
use of a sealant such as Loctite Hydraulic Sealant. Excessive high torquing of
metal fittings may cause a slight shift of the output, but this shift can be
trimmed out by the zero adjustment. Torquing does not significantly affect
linearity or sensitivity.
2.4 Moisture Precautions
The Model 856 is provided with two 1/2” NPT female conduit ports for electrical
termination. These tapered pipe threads are tapped deeper than the NPT
standard, in accordance with industry guidelines. These ports must be sealed
according to standard industry practice, in order to prevent moisture ingress
into the Model 856.
2.5 Venting
The Model 856 is a true gauge pressure transducer. This means that the
reference side of the pressure sensing diaphragm must be vented to atmo-
sphere. If the reference side of the diaphragm were sealed (as in a sealed gauge
transducer), temperature changes would cause the reference pressure to vary.
This may affect the overall accuracy, especially in ranges lower than 500 psig.
The Model 856 provides a vent from the reference side of the sensor to the
inside of the housing and the conduit ports. The user-provided electrical
conduit must be vented to atmosphere in a clean dry location.
(It is important
to prevent moisture ingress from the environment into the wiring chamber
or reference side of the transducer.)
Model 856
Gauge Pressure Transducer
Instruction Bulletin No.203527
4
4.4 Current Output Span Adjustment
Span or full scale output adjustments should only be performed by using an
accurate pressure standard (electronic manometer, digital pressure gauge, etc.)
with at least comparable accuracy to the 856 transducer. With full range
pressure applied to the pressure port, the span may be adjusted by turning the
span potentiometer screw. The factory setting is 20mA (
±
.16mA).
5.0 MODEL 856 PERFORMANCE SPECIFICATIONS
For Ranges
For Ranges
25 PSI and Higher
Less Than 25 PSI
Accuracy RSS
*
(at constant temperature.)
±
.13% FS
±
0.25% FS
Non-Linearity, BFSL
±
0.1% FS
±
0.22% FS
Hysteresis
0.08% FS
0.10% FS
Non-Repeatability
0.02% FS
0.05% FS
*RSS of Non-Linearity, Non-Repeatability and Hysteresis.
Thermal Effects
Compensated Range
°
F(
°
C)
-4 to +176 (-20 to +80)
-4 to +176 (-20 to +80)
Zero Shift %FS/100
°
F (50
°
C)
±
1.0 (
±
0.9)
±
2.0 (
±
1.8)
Span Shift %FS/100
°
F (50
°
C)
±
1.5 (
±
1.4)
±
1.5 (
±
1.3)
Warm-up Shift
±
0.1% FS total
±
0.1% FS total
RETURN POLICY
Returns are accepted on stock items up to 30 days from date of order.
You must contact our Returns Department for a Return Authoriza-
tion (RA) number. Return the goods - freight prepaid - in the original
container and include original packing slip. C. O. D. returns are not
accepted. Gems reserves the right to apply restocking charges.
Tel: 860-793-4357
Fax: 860-793-4563
●
Gems products must be maintained and installed
in strict accordance with the National Electrical
Code and the applicable Gems Product Instruction
Bulletin that covers installation, operating and
proper maintenance. Failure to observe this
information may result in serious injury or
damages.
●
Please adhere to the pressure and temperature
limitations shown throughout this bulletin. These
limitations must not be exceeded. These pressures
and temperatures take into consideration possible
system surge pressures/temperatures and their
frequencies.
Important Points
●
Selection of materials for compatibility with the
media is critical to the life and operation of Gems
products. Take care in the proper selection of
materials of construction, testing is required.
●
Our sensors have been designed to resist shock and
vibration. However, shock and vibration should be
minimized.
●
Our sensors must not be field-repaired.
●
Physical damage sustained by product may render it
unserviceable.
SS2112 Rev
.A 01/03
Gems Sensors
One Cowles Road
Plainville, CT 06062-1198
Toll-Free: 1-800-378-1600
