Operator`s manual

15 SERIAL INPUT
3
3.2 21X/BAROMETER HOOK-UP
Barometer lead wires are provided for two
general types of connections: TTL level output
to the 21X and an RS232 level out put to a
terminal or printer. Of the TTL output
connections, two versions are available for the
21X. Table 1 contains hook-up information for
two 21X configurations and one RS232
terminal/printer configuration. As indicated in
Table 1, the barometer data line must connect
to the HI side of a differential channel. Each
hook-up configuration has specific advantages
as described below.
CAUTION: To avoid damage to the barometer
CMOS chips, make ground connections
first and +12 volts last. All sensor leads not
used in a particular hook-up configuration
should be insulated to avoid possible
shorting.
HOOK-UP CONFIGURATION #1 This hook-up
demands the least power consumption
(typically 1.0 mA quiescent, 6.0 mA active).
If the barometer is jumpered to output the
average of one measurement, the
execution time of Instruction 15 is 0.5 to 0.6
seconds.
HOOK-UP CONFIGURATION #2 This hook-up
demands greater power than Configuration
#1 (typically 5.5 mA quiescent, 6.0 mA
active), yet results in a faster measurement.
If the barometer is jumpered to output the
average of one measurement, Instruction
15 execution time is 0.2 to 0.3 seconds.
HOOK-UP CONFIGURATION #3 The purpose
of this hook-up is to read the barometer on
a standard RS232 device, such as a printer
or terminal instead of the 21X. If failure
occurs, this hook-up allows using a third
device to check if the problem is with the
barometer or with the CR10.
3.3 21X/BAROMETER PARAMETER
CONSIDERATIONS
PARAMETER 3 This parameter specifies
which Digital Control Port is controlling the
barometer, and what type of serial input the
21X will receive. If only the Port number is
entered, a TTL input is implied. A one (1)
before the Port number implies an RS232
input. When Hook-up Configuration #1 or
#2 are used, only the Port number should
be entered.
For multiple repetitions (parameter 1), the
Digital Control Port is sequentially
incremented with each repetition. Thus,
each barometer must connect to a separate
adjacent Port.
PARAMETER 4 This parameter defines the
total number of characters to expect per
repetition.
Instruction 15 requires the use of Intermediate
and Input locations. One Input location is
required per data point. The number of
Intermediate locations consumed is dependent
on the value of Parameter 4. To optimize on
Intermediate locations, Parameter 4 should be
exactly equal to the number of characters per
barometer output (refer to Table 2).