Campbell Scientific AM16/32B AM16/32B Relay Multiplexer - Page 28

AM16/32B Relay Multiplexer # 3 Clock and Delay - With the CR23X and CR10(X) the clock line is connected to a control port. Instruction Do (P86) with the pulse port command (71- 78) pulses the clock line high for 10 ms. Instruction Excitation with Delay (P22) can be added following the Do (P86) to delay an additional 10 ms. When using a 21X or CR7, the clock line may be connected to either an excitation or control port. Connection to an excitation port is preferred because only one instruction Excitation with Delay (P22) is required to send the clock pulse. The instruction should be configured to provide a 10 ms delay with 5000 mV of excitation. A control port can be used to clock the AM16/32B if an excitation port is not available. The 21X and CR7 instruction sequence required to clock with a control port is: instruction Set Port(s) (P20) (set port high), instruction Excitation with Delay (P22) (delay 20 ms without excitation), followed by instruction Set Port(s) (P20) (set port low). # 4 Step Loop Index - With the CR23X, CR10(X), 21X or CR7, instruction Step Loop Index (P90) is used when a measurement instruction within a loop has more than one repetition. This instruction allows 2 - 4 sensors per SET to be measured by 2 - 4 analog input channels. The instruction sends each measurement value to a sequentially assigned input location without overwriting any other current iteration value. Without this instruction, the input location within the loop will advance by only one location per loop iteration even though the measurement instruction's Input Location is indexed. Example: 2 sensors per SET, 6 sensors total; two reps specified in measurement instruction; two measurement values assigned to indexed input locations (--); P90 step of 2. Loop count of three. First pass: Second pass: Third pass: Input locations 1 2 3 4 5 6 1 2 3 4 sensor 5 6 numbers Removing the step loop instruction from the program, the following situation results: First pass: Second pass: Third pass: Input Locations 1 2 3 4 5 6 1 2 3 4 sensor 5 6 numbers Without Step Loop Index (P90) the measurement values for the 2nd and 4th sensors will be overwritten in their input locations. The 1st, 3rd, 5th, and 6th measurement values will reside in the first 4 input locations. Step Loop Index (P90) is available in the CR23X, CR10(X), CR7, and 21X (with 3rd PROM). For 21X dataloggers without 3rd PROM (no instruction Step Loop Index (P90)), a separate measurement instruction (with one rep) is required for each sensor measured within the loop. The input location parameter within both measurement instructions is indexed. For example: 2 sensors per SET; one rep in each of two measurement instructions; two measurement values assigned to indexed input locations (--), one begins with input location 1, the other with input location 4; no Step Loop Index (P90). A total of six sensors to be measured; loop count is three. 18