Teledyne API Model 300M CO Analyzer Instruction Manual, 04033, Rev. A
10.6.3.1 Analog Inputs
16 Analog channels
Analog to Digital (A/D) conversion is accomplished by performing a Voltage to Frequency (V/F) conversion on the input signal at IC U17 and running the frequency output to a counter comprised of IC's U20, U21, U22.
The full scale digital output of the counter section is 80,000 counts, giving an A/D resolution of 1 part in 80,000.
The combination of V/F converter and counter inherently provides an integrating Analog to Digital conversion. The time base for this integration is controlled by the microprocessor using the clock oscillator, U36. Jumper B15 allows the selection of either a 4.0 MHz or 4.8 MHz frequency to minimize electrical pickup at the operating line frequency. Pots R27 and R31 provide offset and gain adjust respectively to the analog input of the V/F converter, allowing the A/D section to be adjusted to match an external voltage standard.
10.6.3.2 Digital to Analog Converters
Four Independent Digital to Analog Converters (DAC's) are contained in IC's U10 and U11 and are used to generate the instrument's analog outputs. These DAC's have 12 bit resolution and are fully buffered by OpAmps at U8 and U9. The outputs of the DAC's are jumper selectable for full scale range at jumpers B6, B7, B8 and B9. The Full Scale Ranges supported are:
0 - 100 mV
0 - 1 V
0 - 5 V
0 - 10 V
In the M300M the use of these four DAC's is:
DAC Channel
Signal
0Strip Chart Analog Output
1DAS Analog Output
2Spare
3Test Function Analog Output
