Due to variances of the electronic components used to create (and protect) the A/D inputs, the voltage that is finally measured by the CPU will be slightly different between various V2 units. FlashScan must be calibrated to compensate for those variations. FlashScan is pre-calibrated at the factory and the end user should never need to perform the calibratration procedure.
If for some reason you need to recalibrate FlashScan, then please read on...
To start the calibration process, connect the FlashScan V2 to the vehicle and to the laptop. In the Scan Tool software, connect to the vehicle and then select the menu option: FlashScan->FlashScan V2 Control Panel. Click on the [Test] button to refresh the A/D counts around 10 times per second. You will see the right-most green LED on FlashScan illuminate. That shows the A/D data is being transmitted from FlashSCan to the laptop.
Behind the scenes:
The voltages measured by FlashScan are converted from raw A/D counts to millivolts using the following transform equation:
millivolts = AD*factor+(Offset*1000)
Where AD is the A/D counts measured by the CPU which will normally range from around 0 (0V) to around 820 (5V).
When you click on the [Initialize] button, FlashScan simply registers the current A/D counts and makes a note of the voltage that you tell it is being supplied. Then when you apply a different (higher) voltage and click the [Calibrate] button, FlashScan performs the following 2 calculations:
1. Calculate the factor:
factor = (ADH-ADL)/(VH-VL)
2. Calculate the offset:
offset = (VL-(ADL*factor))/1000
Where ADL (Low) is the first A/D counts, ADH (High) is the second A/D counts.
VL (Low) is the first voltage, VH (High) is the second voltage.
A Worked example:
Step 1. A 1V (1000mV) signal is fed into FlashScan's AD1 connector, the A/D shows 185 counts. The user enters 1000mV in the "First voltage level" text box and clicks on the [Initialize] button. FlashScan will record ADL as 185 and VL as 1000mV.
No change should be expected in the voltage displayed because FlashScan does not have enough data yet.
Step 2. A 3V (3000mV) signal is fed into FlashScan's AD1 connector, the A/D shows 515 counts. The user enters 3000mV in the "Second voltage level" text box and clicks on the [Calibrate] button. FlashScan performs the following math:
factor = (3000-1000)/(515-185) = 6.0606
offset = (1000-(185*6.0606))/1000 = -0.1212
These two values are immediately applied to the voltage displayed by V2 and you should notice that the voltage measured by V2 will now track to within 10mV of the supplied voltage.
See attached spreadsheet for the actual voltages that will be displayed per A/D count after the above calibration has been completed.
Q. Why should I calibrate FlashScan?
FlashScan is pre-calibrated from the factory and should never need recalibration. The calibration option is available in case an unforseen circumstance arises that requires FlashScan to be recalibrated.
Q. I accidentally changed the calibration settings. How do I restore the factory calibration defaults?
There is no simple way to restore the calibration defaults (yet). You will need to perform the calibration process on each of the AD inputs that were altered.
Q. Why does the second voltage need to be around 4 volts?
It doesn't, the only restrictions on the two voltages that you supply are; they must be 1000mV or more apart and the second voltage must be higher than the first.
Q. I connected a 1.5V signal, entered 1500mV in the "First voltage level" text box and clicked the [Initialize] button. The AD counts showed 247. Why does the factor show 5.0, the offset show 1.0V and the mV show 2230?
The factor, offset and mV values are not computed (i.e. not accurate) until the [Calibrate] button is clicked during the second phase of the calibration process.
Q. I disconnected the 1.5V signal and connected a 3.2V signal. Then I entered 3200mV in the "Second voltage level" textbox and clicked the [Calibrate] button. The AD counts showed 0, the factor showed 5.0, the offset showed 1.0V and the mV showed 1000mV. How do I interpret these results?
The A/D counts should not have been 0 when you applied 3.2V it should have been higher than the 247 that showed when you applied 1.5V in the first step - check the voltage supply and or connections.
The A/D counts (0) is being multiplied by the current factor 5.0 to give 0. Then the current 1000mV offset was added to give 1000mV. But if 3.2V was actually being applied, then the 0 A/D counts is not correct. I would expect it to be showing around 526 counts at 3200mV.
Q. Is the "mV" column the actual millivolts that were read?
Yes, the mV column is the actual mV that FlashScan measures from the attached device, which will almost certainly be wrong until the calibration is complete.
