Pressure Measurement

Differential Pressure Transducer for HVAC – Model 264

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Systems 264 pressure transducers sense differential or gauge (static) pressure and convert this pressure difference to a proportional electrical output for either unidirectional or bidirectional pressure ranges. The 264 Series is offered with a high level analog 0 to 5 VDC or 4 to 20 mA output.

In a typical Setra configuration, a compact housing contains two closely-spaced, parallel, electrically-isolated metallic surfaces, one of which is essentially a diaphragm capable of slight flexing under applied pressure. The diaphragm is constructed of low-hysteresis material such as 17-4 PH SS or a proprietary compound of fused glass and ceramic (Setraceramâ„¢). These firmly secured surfaces (or plates) are mounted so that a slight mechanical flexing of the assembly, caused by a minute change in applied pressure, alters the gap between them (creating, in effect, a variable capacitor). The resulting change in capacitance is detected by a sensitive linear comparator circuit (employing proprietary, custom-designed ASICs), which amplifies and outputs a proportional, high-level signal.

  • Up to 10 PSI overpressure on all ranges
  • Installation time minimized with snap track mounting and easy – to – access pressure ports and eectrical connections
  • 0 to 5 VDC or 2-wire 4 to 20 mA analog outputs are compatible with energy management systems
  • Reverse wiring protection
  • Internal regulation permits use with unregulated DC uower uupplies
  • Fire retardent case (UL 94 V-0 Approved)
  • Meets CE conformance standards
  • Heating, Ventilating and Air Conditioning (HVAC)
  • Energy Management Systems
  • Variable Air Volume and Fan Control (VAV)
  • Environmental Pollution Control
  • Lab and Fume Hood Control
  • Oven Pressurization and Furnace Draft Controls

Technical Details

Performance
 StandardOptional
Accuracy* RSS (At Constant Temp.)±1.0% FS±0.4% FS ±0.25% FS
Non-Linearity, BFSL±0.96% FS±0.38% FS ±0.22% FS
Hysteresis0.10% FS0.10% FS 0.10% FS
Non-Repeatability0.05% FS0.05% FS 0.05% FS
Thermal Effects**
Compensated Range °F(°C) 0 to +150 (-18 to +65)
Zero/Span Shift %FS/°F(°C)±0.033 (±0.06)
Maximum Line Pressure10 PSI
OverpressureUp to 10 PSI in Positive or Negative Direction
Long Term Stability0.5% FS/1 YR
Position EffectRange Zero Offset (%FS/G)
(Unit is factory calibrated at 0g effect in the vertical position.)To 0.5 in. / To 1.0 in. / To 2.5 in. / To 5 in. 0.60 / 0.50 / 0.22 / 0.14
* RSS of Non-Linearity, Hysteresis, and Non-Repeatability.
**Units calibrated at nominal 70°F. Maximum thermal error computed from
this datum.

Environmental Data

Temperature
Operating* °F (°C)0 to +175 (-18 to +79)
Storage °F (°C)-65 to +250 (-54 to +121)
*Operating temperature limits of the electronics only. Pressure media temperature may be considerably higher or lower.

Physical Description

CaseFire-Retardant Glass Filled
Polyester (UL 94 V-0 Approved)
MountingFour screw holes on removable
zinc plated steel base (designed
for 2.75” snap track)
Electrical ConnectionScrew Terminal Strip
Pressure Fittings3/16” O.D. barbed brass pressure fitting for 1/4” push-on tubing
Zero and Span AdjustmentsAccessible on top of case
Weight (Approx.)10 ounces

Pressure Media

Typically Air or Similar Non-Conducting Gases

Electrical Data (Voltage)

Circuit 3-Wire (Com, Exc, Out)
Excitation9 to 30 VDC
Output*0 to 5 VDC**
Bidirectional Output at Zero Pressure 2.5 VDC**
Output Impedance 100 ohms
*Calibrated into a 50K ohm load, operable into a 5000 ohm load or greater.
**Zero output factory set to within ±50mV (±25 mV for optional accuracies).
**Span (Full Scale) output factory set to within ±50mV. (±25 mV for optional accuracies).

Electrical Data (Current)

Circuit2-Wire
Output*4 to 20 mA**
Bidirectional Output at Zero12 mA**
External Load0 to 800 Ohms
Minimum supply voltage (VDC) = 9+ 0.02 x (Resistance of receiver plus line).
Maximum supply voltage (VDC) = 30+ 0.004 x (Resistance of receiver plus line).
*Calibrated at factory with a 24 VDC loop supply voltage and a 250 ohm load.
**Zero output factory set to within ±0.16mA (±0.08 mA for optional accuracies).
**Span (Full Scale) output factory set to wtihin ±0.16mA (±0.08 mA for
optional accuracies).

Note: Specification are Subject to change without notice