Setra Systems 265 Installation Manual page 2

Diagram 1
SPAN
ADJUSTMENT
ZERO
ADJUSTMENT
+EXC
-COM
OUT
3.2 Current Output Units
The Model 265 is a two-wire loop-powered 4 to 20mA current output unit (see
Diagram 3). The current flows into + terminal and returns back to the power
supply through the - terminal (see Diagram 3). The power supply must be a
DC voltage source with a voltage range between 9 and 30 measured between
terminal + and - terminals. The unit is calibrated at the factory with a 24 VDC
loop supply voltage and a 250 ohm load.
CurrentCircuit Diagram
9 to 30 VDC
4.0. CALIBRATION
The 265 transducer is factory calibrated and should require no field adjust-
ment. Generally, the mounting position will have a zero shift effect on ranges
below 1" WC. Whenever possible, any zero and/or span offsets should be
corrected by software adjustment in the user's control system. However, both
zero and span adjustments are accessible either on the front of the unit or by
removing the optional conduit enclosure. The 265 transducer is calibrated in
the vertical position at the factory.
4.1 Voltage Output Zero Adjustment
While monitoring the voltage between the positive output (OUT) and
common (COM), and with both pressure ports open to atmosphere, the zero
may be adjusted by turning the zero adjustment screw. (See Diagram 1 for
2
Voltage Circuit Diagram
- COM
Readout
or Model
OUT
DAS
Power
+ EXC
Supply
Diagram 2
Connected to positive terminal of
DC/AC power supply
Connect as the reference for power
supply and output signal
Connect to positive terminal of control
or pressure
+
265
_
Current
Monitoring
Device
location of zero adjustment.) For 0-5 VDC output units, the factory settings
are 0.0VDC (±50mV) for unidirectional pressure ranges and 2.5VDC (±50mV)
for bidirectional pressure ranges. Optional outputs are set at the same ±1%
factory setting.
265
4.2 Voltage Output Span Adjustment (Complete the zero adjustment
before setting span.)
Span or full scale output adjustments should only be performed by using an
accurate pressure standard (electronic manometer, digital pressure gage, etc.),
with at least comparable accuracy to the 265 transducer (<±1% FS). With full
range pressure applied to the high pressure port (reference port open to atmo-
sphere), the span may be adjusted by turning the SPAN adjustment screw. (See
Diagram 1 for location of the SPAN adjustment.) For 0-5 VDC output units, the
factory settings are 5.0 VDC (±50mV) for unidirectional and bidirectional ranges.
Optional outputs are set at the same ±1% factory setting.
4.3 Current Output Zero Adjustment
While monitoring the current output between +EXC and OUT, and with both
pressure ports open to atmosphere, the zero may be adjusted by turning the
zero adjustment screw. (See Diagram 1 for location of zero adjustment.) The
factory settings are 4mA (0.16mA) for unidirectional pressure ranges and 12mA
(0.16mA) for bidirectional ranges.
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 gage,
etc.) with at least comparable accuracy to the 265 transducer (<±1% FS). With
full range pressure applied to the high pressure port (reference port open to
atmosphere), the span may be adjusted by turning the SPAN adjustment screw.
(See Diagram 1 for location of SPAN adjustment.) The factory settings are 20mA
(0.16mA) for unidirectional and bidirectional pressure ranges.
5.0 MODEL 265 PERFORMANCE SPECIFICATIONS
Accuracy RSS
(at constant temperature.)
Non-Linearity, BFSL
Hysteresis
Non-Repeatability
*RSS of Non-Linearity, Non-Repeatability and
Hysteresis.
Position Effects
(Unit is factory calibrated at 0g effect in the vertical position)
Range
0 to 1" WC
0 to 5" WC
0 to 30" WC
* ±1.0% FS Thermal Effects
Compensated Range °F(°C)
±0.98% FS Zero/Span Shift %FS/°F(°C)
0.1% FS Maximum Line Pressure
0.05% FS Overpressure
Warm-up Shift
Zero Offset (%FS/G)
.22
.14
.06
0 to +150 (-18 to +65)
0.033 (0.06)
10 PSI
Up to 10 PSI
(range dependent)
±0.1% FS total
3