Diamond Power Products MM-48-AT user manual Analog Input Ranges and Resolution

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7. ANALOG INPUT RANGES AND RESOLUTION

7.1 Resolution

Diamond-MM-48-AT uses a 16-bit A/D converter. This means that the analog input voltage can be measured to the precision of a 16-bit binary number. The maximum value of a 16-bit binary number is 216 - 1, or 65535, so the full range of numerical values that you can get from a Diamond-MM-48-AT analog input channel is 0 - 65535.

The smallest change in input voltage that can be detected is 1/(216), or 1/65536, of the full- scale input range. This smallest change results in an increase or decrease of 1 in the A/D code, and so this change is referred to as 1 LSB, or 1 least significant bit.

7.2 Input Ranges

Diamond-MM-48-AT is available in two models. The default model has bipolar inputs of +/- 10V and +/-5V, selectable with jumper block J10. An optional model with a slightly different component configuration has unipolar inputs of 0-5V.

7.3 Single Ended and Differential Inputs

A single-ended input is a two-wire input (one input signal and ground) that is referenced to analog ground on the board. This means that the input voltage will be measured with respect to the board’s analog ground. A differential input is a three-wire input (input +, input -, and ground), and the board will measure the difference between the voltages of the two inputs. Diamond-MM-48-AT works only with single-ended inputs.

In some cases, a differential input can be simulated by connecting the high and low input wires to two adjacent analog input channels, measuring both of them with and A/D scan operation, and subtracting the low reading from the high reading. This will work only for very slow changing (or DC) signals with very low noise. The problem with this technique is that the two signals are sampled at different times, either 5µs or 9.3µs apart depending on the setting of the SCANINT register bit. This time delay can lead to measurement errors due to the change in the input signal during the delay. For example, an input signal consisting of a 1KHz sine wave with 10V amplitude has a maximum slope of 10V x 2 x π x 1000Hz = 63,000 V/sec, or 63 mV/µs. This represents a change of 315mV during the 5µs delay between the sampling of the high input and the low input. For a 16-bit A/D converter on a +/-10V input range, this is an error of over 1,000 counts.

Diamond-MM-48-AT User Manual V1.01

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Contents DIAMOND-MM-48-AT Table of Contents Description DIAMOND-MM-48-AT Board Drawing Signal Name Definition O Header Pinout and PIN DescriptionJ3 Analog and Digital I/O Signal Name Definition Relay output contacts J4 Relays and OptocouplersOptoisolated input contacts Interrupt Level Selection Board ConfigurationBase Address Base Address Jumper Position Hex DecimalOptocoupler Polarity ReservedAnalog Input Range Overview Base + Write Function Read FunctionLSB MSB Read operations Register Map Bit AssignmentsWrite operations DA7 DA6 DA5 DA4 DA3 DA2 DA1 DA0Base + Read Register DefinitionsBase + Write DefinitionsAD9 AD8 Base + Read/Write A/D Channel RegisterHIGH3 HIGH2 HIGH1 HIGH0 LOW3 LOW2 LOW1 LOW0 DIR3 DIR2 DIR1 DIR0 Base + Read/Write Digital I/O Configuration RegisterBase + Read/Write Relay Control Port RELAY7 RELAY6 RELAY5 RELAY4 RELAY3 RELAY2 RELAY1 RELAY0OEN3 OEN2 OEN1 OEN0 POL3 POL2 POL1 POL0 DIO3 DIO2 DIO1 DIO0Base + Read Digital I/O Data and Edge Status DEDGE3 DEDGE2 DEDGE1 DEDGE0 DIO3 DIO2 DIO1 DIO0Base + Write Channel and Control Register Daupdt DACH2 DACH1 DACH0OEDGE3 OEDGE2 OEDGE1 OEDGE0 OPTO3 OPTO2 OPTO1 OPTO0 Dapre Daprld Reset Fiforst Adstart Base + Write Command RegisterPOL ADCH3 ADCH2 ADCH1 ADCH0 Base + Read Status RegisterCKSEL1 CKFRQ1 CKFRQ0 Scnint Clken Clksel Base + Write Configuration RegisterAdbusy Dabusy CKSEL1 CKFRQ1 CKFRQ0 Scnint Clken Clksel Base + Read Configuration & Status RegisterOVF Fifoth Fifoen Scanen Base + Write Fifo Control RegisterFifoth Fifoen Scanen Base + Read Fifo Status RegisterClrt Clrd Clro Clra Tinte Dinte Ointe Ainte Base + Write Interrupt Control RegisterTint Dint Oint Aint Tinte Dinte Ointe Ainte Base + Read Interrupt Status RegisterBase + Read/Write Counter/Timer D7 Base + Read/Write Counter/Timer D15Base + Read/Write Counter/Timer D23 Base + Write Counter/Timer Control Register Ctrno Latch Gtdis Gten Ctdis Cten Load CLRCtrno Base + Read/Write Eeprom / TrimDAC Address Register Base + Read/Write Eeprom / TrimDAC Data RegisterBase + Read Fpga Revision Code Base + Write Eeprom Access Key RegisterBase + Write Calibration Control Register Base + Read Calibration Status RegisterSingle Ended and Differential Inputs Analog Input Ranges and ResolutionResolution Input RangesPerforming AN A/D Conversion LSB = readbase MSB = readbase+1 Data = MSB * 256 + LSB Trigger an A/D conversion on the current channelInput voltage = A/D value / 32768 * Full-scale voltage Conversion or Scan D SCAN, FIFO, and Interrupt OperationTrigger Clken ClkselFifoen = Fifo OperationInterrupt Operation Fifoen Fifoth ScanenGuidelines for Selecting Fifo Use Fifoen and Fifoth Operation TableAinte Fifoen Scanen Analog Output Overview Generating AN Analog Output 12.3 D/A Calibration Autocalibration OperationReference Voltages 12.2 A/D calibrationDigital I/O Operation Optocoupler Operation Procedure for enabling interrupts on selected edgesPolarity and logic readback Edge detection assumes OENn = 1 to enable edge detectionRelay Operation COUNTER/TIMER Operation Counter 0 A/D Sample ControlCounter 1 Counting/Totalizing Functions Counter Command SequencesCounter Outpbase+15,0x01 Outpbase+15,0x81 Specifications AutocalibrationGeneral
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