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IRIS7P-CO2 for carbon dioxide
发布时间：2010-06-21 编辑人：管理员
Sensors operate using the proven Non Dispersive Infrared (NDIR) principle to detect and monitor the presence of target gas.
产品价格： 面议
起购数量： 1
FEATURES
IRIS7P – CO2 for carbon dioxide.
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Standard Sensor Size.
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Fast Response.
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Internal Temperature signal.
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Rugged construction.
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Temperature compensated detector elements.
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Wide operating temperature and humidity range.
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Low power.
DESCRIPTION
Sensors operate using the proven Non Dispersive Infrared (NDIR) principle to detect and monitor the presence of target gas. The sensor contains an infrared source, an optical cavity into which gas diffuses, a dual temperature compensated infrared detector and a thermistor to monitor the internal temperature of the sensor.
The IR light is capable to excite higher energy levels (excited states) of the molecules (rotational or vibrational excitations) by coupling to the dipole moment of the heteroatomic assembly. Heat energy from the IR light is therefore transferred into the gas – it heats up. Concomitantly, the intensity of a beam of IR light, which passes through a gas volume, diminishes. The intensity loss is a function of the number of active gas molecules in the volume, which means a function of the gas concentration.
It may be necessary to modulate the light source, turning it on and off at a specific frequency, because of Pyroelectric detectors respond only to changes in light level.
The infrared pyrodetector provide two output signals in response to pulsed incident radiation, at the same frequency:
- Active : Sinusoidal output from a narrow bandpass filter tuned to the target gas and and decrease with target gas.
- Reference: Sinusoidal output from neutral filter for background monitoring.
The outputs of the Active and Reference signals must be monitored continuously to obtain their peak-to-peak values.
By taking the ratio of Active to Reference peak to peak signals, the user can discriminate the target gas.
SPECIFICATION IRIS7P – CO2 (0-5% Vol.)
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Control
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Required Specification
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D.C. Power Voltage:
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5V d.c. on pin Vdd
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Lamp Power:
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- Voltage: 0- 5V (50% duty-cycle) on pin Lamp+.
- Power requirements: 0- 60mA max (50% duty-cycle).
- Lamp drive frequency : 2.0Hz minimum, 3.0 Hz typical, 4.0 Hz maximum.
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Active pk-pk out @ 0 gas
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4,5 mV @ 3 Hz
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Reference pk-pk out @ 0 gas
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1,2 mV @ 3 Hz
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Pinout Format
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7 pins standard for base form
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Working Temperature
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-40’C to +50’C
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Humidity Range
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0-95% non condensing
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Gas types
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Carbon Dioxide
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Repeatability
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<+/-2% of range
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Resolution
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<2% of range
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Long Term Drift
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<+/-3% of range/year
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Response Time T90 CO2
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<30secs in target housing with 3mm 120um sinter
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EMC
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To enable use in a detector which meets EN 50270
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Measuring Range
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0-5%vol Carbon Dioxide
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MTBF
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≥ 5 years
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Weight
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44 grams
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MECHANICAL DETAIL
CALIBRATION
When installed, the sensor require the calculation of the Zero and Span values (calibration). The Linearization is performed during the calculation using the “b” and “c”
coefficients, and is based upon the Beer-Lambert Law.
- Calculate the “Zero”
The following calculation is performed when the gas sensor is being exposed to the zero test gas (i.e. nitrogen), without the presence of the target gas.
Zero = Act / Ref
Where:
Act = the peak- to-peak output of the Active Detector in volts in zero test gas.
Ref = the peak-to-peak output of the Reference Detector in volts in zero test gas.
- Calculate the “Span”
The following calculation is performed when the gas sensor is being exposed to the calibration test gas.
Span = [1 – Act / (Zero x Ref)] / [1 – exp(–b*X^c)]
Where:
Act = the peak-to-peak output of the Active Detector in volts in the calibration test gas.
Ref = the peak-to-peak output of the Reference Detector in volts in the calibration test gas.
Zero = the “Zero” value (stored) calculated during this calibration routine.
b = fixed linearization coefficient.
c = fixed linearization coefficient.
X = the concentration of the applied calibration test gas in % Volume.
- Calculate the “Target Gas Concentration”
Gas =({–ln [1 – (1 – Act / (Zero x Ref)) / Span)]} / b)^(1 / c)
Where “(1 – Act / (Zero x Ref))” is called Absorbace Response.
Configuration DATA
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b:
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1,06044
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c:
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0,677166
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