Campbell Scientific CR10 CR10 Measurement and Control - Page 127

There is also an option to output the count as a frequency (i.e., counts/execution interual in seconds = Hz) as well as discard the result from an excessive interual. This allows the use of a conversion factor that is independent of the execution interval. The options of discarding counts from long interuals, pulse input type, and using a 16 bit counter are selected by the code entered for the 4th parameter (Table 9-2). NOTE: Allpulse count instructions must be kept in the same table. lf the Pulse Count lnstruction is contained within a subroutine, that subroutine must be called from Table 2. TABLE 9-2. Pulse Count Configuration Codes Gode 0 1 2 3 4 1X 2X Confiouration High frequency pulse Low levelAC Switch closure High frequency pulse, sixteen bit counter Low levelAC, sixteen bit counter Long interval data discarded Long interval data discarded, frequency (Hz) output PARAM. DATA NUMBER TYPE DESCRIPTION 01: 2 Repetitions 02: 2 Pulse channel number for first measurement 03: 2 Configuration code (from above table) o4; 4 Input location for first measurement 05: FP Multiplier 06: FP Otfset Input locations altered: 1 per measurement Intermediate storage locations altered: 1 for each repetition SECTION 9. INPUT/OUTPUT INSTRUCT]ONS *** 4 EXCITE, DELAY, AND MEASURE *** FUNCTION This instruction is used to apply an excitation voltage, delay a specified time, and then make a single-ended voltage measurement. A 1 before the excitation channel number (1X) causes the channelto be incremented with each repetition. PARAM. DATA NUMBER TYPE 01: 2 02: 2 03: 2 o4: 2 05: 4 06: 4 07: 4 08: FP 09: FP DESCRIPTION Bepetitions Range code (Table 9-l) Single-ended channel number for first measurement Excitation channel number Delay in hundredths of a second Excitation voltage (millivolts) Input location number for first measurement Multiplier Offset lnput locations altered: 1 per measurement **. 5 AC HALF BRIDGE *** FUNCTION This instruction is used to apply an excitation voltage to a half bridge (Figure 13.5-1), make a single-ended voltage measurement of the bridge output, reverse the excitation voltage, then repeat the measurement. The difference between the two measurements is used to calculate the resulting value which is the ratio of the measurement to the excitation voltage. A 1 before the excitation channel number (1X) causes the channelto be incremented with each repetition. The excitation "on time" for each polarity is exactly the same to insure that ionic sensors do not polarize with repetitive measurements. The range should be selected to be a fast measurement (range 11-15), limiting the excitation on time to less than 800 microseconds at each polarity" A slow integration time should not be used with ionic sensors because of polarization error. 9-3