Campbell Scientific EC150 CO2 and H2O Open-Path Gas Analyzer and EC100 Electronics with Optional CSAT3A 3D Sonic Anemometer - Manual (Page 67)

Appendix C. Alternate EC100 Outputs
//signature(), signature algorithm.
// Standard signature is initialized with a seed of 0xaaaa.
// Returns signature.
unsigned short signature( unsigned char* buf, int swath,
unsigned short seed ) {
unsigned char msb, lsb;
unsigned char b;
int i;
msb = seed >> 8;
lsb = seed;
for( i = 0; i < swath; i++ ) {
b = (lsb << 1) + msb + *buf++;
if( lsb & 0x80 ) b++;
msb = lsb;
lsb = b;
}
return (unsigned short)((msb << 8) + lsb);
}
C.2 Analog Output
C.2.1 Specifications
Analog (two outputs for CO
2
and H
2
O densities)
Voltage range: 0 mV to 5000 mV
Resolution: 76 µV (16 bit)
Update rate: 100 Hz
Accuracy (at 25°C): ± 3 mV
CO
2
density equation: mg·m -3 = 0.38632· (mV
out
) − 102.59
Full scale range: − 103 to 1829 mg·m -3
H
2
O density equation: g·m -3 = 0.00865· (mV
out
) − 2.26
Full scale range: − 2 to 41 g·m -3
C.2.2 Detailed Information
Although digital outputs are generally preferred, analog outputs are available
on the EC100 for compatibility with simple recording devices that cannot use
the digital outputs. Analog outputs are subject to additional noise and
digitization errors. Digital outputs include additional diagnostic data to assist
with data quality assessment and troubleshooting. If analog output is enabled,
the EC100 will output two analog signals that correspond to CO
2
density and
H
2
O density. These signals range from 0 to +5 V. TABLE C-2 gives the
multipliers and offsets for the analog outputs.
Analog output may also be used, however only CO
2
density and H
2
O density
will be output. For analog output, use cable CABLE2TP-L (pn 26986-L), the
length of which is specified by the user when ordering. The connector labeled
Analog Outputs on the EC100 panel indicates where each wire should be
connected (CO
2
voltage signal, H
2
O voltage signal, and two ground
connections).
C-3