Teledyne M300EM User Manual

5.9. CARBON DIOXIDE SENSOR (OPTION 67A) 

The optional CO

2

 sensor allows the M300E/EM to measure both CO and CO

2

 simultaneously.  This option 

includes a CO

2

 sensor probe, a Logic PCA that conditions the probe output and issues a 0-5 VDC signal to the 

analyzer’s CPU that is used to compute the CO

2

 concentration.   

The M300E/EM receives this input, scales it based on the values of the CO

2

_SLOPE and CO

2

_OFFSET 

recorded during calibration (see Section 9.7.2). 

 

Figure 3-4 shows the location of the Sensor Probe and PCA within the M300E/EM. 

The CO

2

 sensor assembly itself does not have any serviceable parts and is enclosed in an insulated canister. 

 

5.9.1. CO

0-20%

 

M300EM

 

 

Accuracy at 25˚C 0.02% CO + 2% of reading 

Linearity 0.5 % of full scale 

Typical Temperature Dependence  -0.1% FS / ˚C 

Long Term Stability <+15 % FS / 2 years 

Response time  20 seconds 

Warm up time  5 minutes 

Power consumption 2.5 watts 

 

5.9.2. THEORY OF OPERATION 

5.9.2.1. NDIR measurement of CO

The optional CO

2

 sensor is a silicon based Non-Dispersive Infrared (NDIR) sensor.  It uses a single-beam, dual 

wavelength measurement method. 

An infrared source at one end of the measurement chamber emits IR radiation into the sensor’s measurement 
chamber where light at the 4.7 μm wavelength is partially absorbed by any CO

2

 present.  A special light filter 

called a Fabry-Perot Interferometer (FPI) is electronically tuned so that only light at the absorption wavelength of 
CO

2

 is allowed to pass and be detected by the sensor’s IR detector. 

A reference measurement is made by electronically shifting the filter band pass wavelength so that no IR at the 
CO

2

 absorption wavelength is let through.   

04288D DCN5752