Difference between revisions of "826"
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| + | ===Calibration errors caused by missing shunt=== | ||
On 826 SDKs earlier than version 3.2.0, analog calibration values will not be applied without J6 (labeled "Calibration Enable") installed. A missing shunt is intended to protect against accidental overwriting of calibration values, but in these SDKs it also prevents the reading of those values. This is resolved in SDK version 3.2.0 and above; in these versions the shunt functions as intended and must be installed only when calibrating the board (though leaving it installed all the time is okay). | On 826 SDKs earlier than version 3.2.0, analog calibration values will not be applied without J6 (labeled "Calibration Enable") installed. A missing shunt is intended to protect against accidental overwriting of calibration values, but in these SDKs it also prevents the reading of those values. This is resolved in SDK version 3.2.0 and above; in these versions the shunt functions as intended and must be installed only when calibrating the board (though leaving it installed all the time is okay). | ||
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If board calibration is incorrect, make sure J6 is installed or upgrade to SDK version 3.2.0 or higher. The 826 SDK can be downloaded from the [http://www.sensoray.com/products/826.htm 826 product page]. | If board calibration is incorrect, make sure J6 is installed or upgrade to SDK version 3.2.0 or higher. The 826 SDK can be downloaded from the [http://www.sensoray.com/products/826.htm 826 product page]. | ||
| − | == | + | ===Apparent nonlinearity=== |
[[File:AdgGroundReference.gif|thumb|300px|To prevent high CMV, connect isolated source to ADC ground.]] | [[File:AdgGroundReference.gif|thumb|300px|To prevent high CMV, connect isolated source to ADC ground.]] | ||
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If you are using an isolated source, be sure to connect one side of the source to the ADC power supply ground as shown in the diagram to the right. This will prevent high CMV that might othewise result in apparent non-linearity or calibration errors. | If you are using an isolated source, be sure to connect one side of the source to the ADC power supply ground as shown in the diagram to the right. This will prevent high CMV that might othewise result in apparent non-linearity or calibration errors. | ||
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| + | ==Counters== | ||
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| + | ===Snapshot counts upon match=== | ||
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| + | When a snapshot is caused by counts equal to a compare register, the snapshot counts will always be equal to the compare register value. | ||
Revision as of 08:51, 27 March 2014
Contents |
ADC
Calibration errors caused by missing shunt
On 826 SDKs earlier than version 3.2.0, analog calibration values will not be applied without J6 (labeled "Calibration Enable") installed. A missing shunt is intended to protect against accidental overwriting of calibration values, but in these SDKs it also prevents the reading of those values. This is resolved in SDK version 3.2.0 and above; in these versions the shunt functions as intended and must be installed only when calibrating the board (though leaving it installed all the time is okay).
If board calibration is incorrect, make sure J6 is installed or upgrade to SDK version 3.2.0 or higher. The 826 SDK can be downloaded from the 826 product page.
Apparent nonlinearity
Many of our customers have observed ADC nonlinearity during development and discovered that that it was caused by excessive common-mode voltage (CMV). This often happens when the ADC is used to measure an isolated voltage source such as a battery, thermocouple, or isolated power supply. Since the source is isolated, the CMV may float up or down until it exceeds the maximum allowed CMV of the ADC's input circuitry.
If you are using an isolated source, be sure to connect one side of the source to the ADC power supply ground as shown in the diagram to the right. This will prevent high CMV that might othewise result in apparent non-linearity or calibration errors.
Counters
Snapshot counts upon match
When a snapshot is caused by counts equal to a compare register, the snapshot counts will always be equal to the compare register value.