Campbell Scientific CR5000 CR5000 Measurement and Control Module - Page 168
SDMSpeed (BitPeriod), SDMTrigger, SIO4 (Dest, Reps, SDMAddress, Mode, Command, Param1, Parameter
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Section 7. Measurement Instructions Parameter & Data Type CaptureTrig Constant, Variable, or Expression Mult, Offset Constant, Variable, Array, or Expression Enter This argument is used when the "Capture All Events" output option is used. When CaptureTrig is true, the INT8 will return the last nnnn events. A multiplier and offset by which to scale the raw results of the measurement. See the measurement description for the units of the raw result; a multiplier of one and an offset of 0 are necessary to output in the raw units. For example, the TCDiff instruction measures a thermocouple and outputs temperature in degrees C. A multiplier of 1.8 and an offset of 32 will convert the temperature to degrees F. SDMSpeed (BitPeriod) Changes the rate that the CR5000 uses to clock the SDM data. Slowing down the clock rate may be necessary when long cables lengths are used to connect the CR5000 and SDM devices. Parameter & Data Type BitPeriod Constant or variable Enter The time per bit, in microseconds. Initial Setting (default): 30.0 µS Resolution: 50 µS Min Setting: 8 µS Max Setting 3 mS SDMSpeed(30) gives: 30.0 µS SDMSpeed(k) gives: bit_rate = INT(k*20) * Resolution When calculating SDMSpeed(k), the loggers round down to the next higher bit rate. SDMTrigger When SDMTrigger is executed, the CR5000 sends a "measure now" group trigger to all connected SDM devices. SDM stands for Synchronous Device for Measurement. SDM devices make measurements independently and send the results back to the datalogger serially. The SDMTrigger instruction allows the CR5000 to synchronize when the measurements are made. Subsequent Instructions communicate with the SDM devices to collect the measurement results. Not all SDM devices support the group trigger; check the manual on the device for more information. SIO4 (Dest, Reps, SDMAddress, Mode, Command, Param1, Param2, ValuesPerRep, Multiplier, Offset) The SIO4 instruction is used to control and transmit/retrieve data from a Campbell Scientific SIO4 Interface (4 Channel Serial Input/Output device). See the SDM-SIO4 Serial Input Interface manual for operation details. 7-42