Installation Guide
Alpha Instruments Model 165
Differential Pressure Transducers
Every Model 165 has been tested and calibrated before shipment.
Alpha Instruments M165 pressure transducers sense differential or gauge (static) pressure and convert this
pressure difference to a proportional high level analog output for both unidirectional and bidirectional pressure
ranges. Three standard output versions are offered: Voltage output of 0 to 5 VDC, 0 to 10VDC and current
ou
tput of 4 to 20mA.
Media Compatibility：
Model 165 transducers are designed to be used with air or nonconducting gases. Use with liquids or corrosive
gases will damage the unit.
Environmental Requirement：
Operating Temperature 0 ～ 170
o
F (-18 ～ 77℃)
Compensated Temperature Range 40 ～ 170
o
F (4 ～ 77℃)
Temperature Drift ＜0.025%FS/
o
F (＜0.045%FS/℃)
Pressure Fittings：
The Model 165 is designed to be used with 3/16” I.D. push-on tubing. The positive (high) pressure port and the
reference (low) pressure port are labeled " + "and " - " respective
ly. For best results (shortest response times),
3/16” I.D. tubing is suggested for tubing lengths up to 80 feet (25 meters), 1/4” I.D. for tubing lengths up to 250
feet (75 meters), and 3/8” I.D. for tubing lengths up to 720 feet (220 meters).
Electrical Installation（
Voltage Output）
：
The Model 165V is a 3-wire circuit, with three terminals available for wiring. These terminals have the
designation “ + ”, “ O ” and “ - “ (See Diagram 1). The power supply and signal references are commend on the
circuit (See Diagram 2).
The model 165V has a 0-5 or 0-10 VDC output. (See Diagram2).
The 165V can operate from 12-32VDC excitation. The unit is calibrated at the factory with a 24 VDC power,
50KΩ load resistor.
"+"：Connect to positive terminal
of DC power supply.
"O"：Connect to positive terminal of control or pressure
monitor.
"-"：Connect as the reference for power supply and
output signal.
Electrical Installation(Current Output)：
The Model 165C is a two-wire loop-powered 4 to 20mA current output unit and delivers rated current into any
external load of 0 to 1000 ohms. These terminals have the designation of “+” and “-“ (See Diagram 3). The
current flows into the + terminal and returns back to the power supply through the - terminal (See Diagram 4).
The 165C can operate from 12-32VDC excitation. The unit is calibrated at the factory with a 24 VDC loop supply
voltage and a 250oh
m load.
The below table shows the maximum wire and receiver resistances as a function of supply voltage.
V
min
V
max
R
min
R
max
RL at Supply Voltage (Vs)
12 32 0 1000 RL≤50(Vs-12)
For Example：Voltage is 24VDC，RL≤50(24-12)=600Ω，the load resistance should not exceed 600Ω。
Voltage Circuit Diagram
165V
+ EXC + OUT
EXC
Readout
or
DAS
Power
Supply
Dia
ram 1
Diagram 2
Current Circuit Diagram
165C
+ EXC
Current
Monitoring
Device
Power
Supply
EXC
4 margaiD3 margaiD
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