MicroBrick I/O - Industrial Control Links

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MicroBrick Distributed I/O Modulesrepresents an input of approximately 5Vdc. If the current configuration switches areenabled, the input current can be calculated as the voltage drop read across aprecision 121ohm resistor, or just over 40mA for a full scale readings of 65,535. Thecalculation is:A/D Reading = (65535 * mA * 121) /5If the current sources are enabled (for resistance measurements), the RAW readingsare the ratiometric values read across the input resistance in series (bottom portion ofa voltage divider) with a precision 20,000 ohm 0.1% low-drift resistor connected to theA/D reference. The calculation is:A/D Reading = 65535 * R / ( R + 20,000)where R is the input resistance being measured. For example, a 10,000 resistor willread approximately 21845 counts:65535 * 10,000/(10,000 + 20,000) = 218455Vdc ModeWhen configured for voltage measurements, the Universal Input module measuressignals from 0 to 5.6 volts (5 volts plus 12% over-range) with a resolution of just over16-bits. There’s no loss of accuracy in this over-range area, so it’s possible toaccurately read the signal levels from slightly misadjusted sensors that run “a littlehot”. It’s also possible to distinguish between a sensor output that is at full scaleversus over-range. The Universal Input module scales and performs calibrationcorrection on the readings, so that a full scale reading of 5.6Vdc is presented to theHost system as a value of 56000 (10,000 counts per volt). This provides readings thatwithout further scaling, read out directly in 100uV increments (imagine a decimalpoint 4 places from the right to interpret the readings in volts).20mA ModeWhen configured for milliampere measurements, the Universal Input modulemeasures signals from 0 to just over 40mA (200% over-range for “standard” 20mAsignals). The module scales and performs calibration correction on the readings, sothat a full scale reading of 40mA is presented to the main CPU as a value of 40000(1,000 counts per milliampere). The milliampere mode is typically used to measure theoutput of 4 to 20mA sensors. The readings from these sensors will come back to theHost system as 4000 for 4mA and 20,000 for 20mA. Current is measured by readingthe voltage drop across a 121 ohm precision resistor. Besides setting the input modein the module, current loops require that the current sense resistors be enabled bysetting a DIP switch (labeled 20mA) next to their respective input connector. There is aseparate switch for each input.Millivolt ModeThe MicroBrick Universal Input module can accurately measure very small signallevels like those from “bridge” type pressure transducers and low power devices such asolar radiation sensors. In the millivolt mode, the module has a full scalemeasurement range of +/-300mV. The microprocessor in the Universal Input module50Copyright © 2007 Industrial Control Links, Inc. All Right Reserved
MicroBrick Distributed I/O Modulesscales and performs calibration correction on the low-level readings, so that a fullscalereading of +/- 300mV is presented back to the Host system as a value of +/-30,000 (10,000 counts per 100mV). Besides reading the output of low-level sensors,this mode is useful for creating custom input voltage ranges using an external resistorvoltage divider.Typical custom ranges and theircorresponding divider values are listedbelow. The resistor values shownprovide approximately a 150% overrange capacity ( +/-200mV signal forlisted To Analog Input full-scale values)values were also chosen to provide aohm or higher resistance on the inputsignal.From Analog Sensor"Upper"Resistor"Lower"ResistorTo Analog InputtheThe10KRange “Upper” resistor “Lower” resistor+/-1Vdc 8.06K ohm 1% 2.0K ohm 1%+/-5Vdc 12.1K ohm 1% 499 ohm 1%+/-10Vdc 24.3K ohm 1% 499 ohm 1%Thermocouple ModesThe MicroBrick Universal Input module supports temperature measurements usingthermocouple sensors. No external signal conditioners are needed for any combinationof type J, K, T, E, R, S, B and N thermocouples.Thermocouple signals require linearization and cold-junction compensation. In theMicroBrick Universal Input module, the cold junction (terminal block) temperature ismeasured by a pair of solid-state temperature sensors, one located in close proximityto each I/O terminal block. The temperature readings from these sensors are availablein a pair of Modbus registers that can also be viewed near the bottom of the AnalogInputs window in the ScadaFlex I/O toolbox software as shown below.Cold JunctionTemperaturesThe microprocessor in the MicroBrick Universal Input module automatically performsthe required compensation and linearization calculations so that an accurate scaledand calibrated temperature reading in degrees C or degrees F is provided back to theHost system. The inputs have upscale burnout protection, forcing a maximumtemperature reading for an open thermocouple sensor. The supported temperatureranges and corresponding readings for each of the thermocouple types are listedbelow:Thermocouple Temperature Range From UI ModuleCopyright © 2007 Industrial Control Links, Inc. All Right Reserved51
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Page 53 and 54: Type II - Deg C -40.1ºC to 203.4º
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Page 59 and 60: Register Map - Universal Input UI8I
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Page 65 and 66: Modbus Register MapSTATUS (Read Onl
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Page 71 and 72: Combo I/O ModulesMicroBrick Distrib
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Page 77 and 78: Register Map - Combo I/O MicroBrick
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MicroBrick I/O - Industrial Control Links

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