Teledyne 300M Instruction Manual page 107

Teledyne API Model 300M CO Analyzer Instruction Manual, 04033, Rev. A
10.6.3.1 Analog Inputs
16 Analog channels (0-5 VDC) are multiplexed under microprocessor control by IC U26 and
transmitted via buffer amp U29 to the V/F converter section of the board for A/D conversion.
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
0
1
2
3
Signal
Strip Chart Analog Output
DAS Analog Output
Spare
Test Function Analog Output
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