ABS (Automated BOCLE System)
/ Calibration
Introduction
There are very few calibration procedures needed to be taken for the ABS.
Switch on the instrument as normal and allow 15 minutes for the internal temperatures to stabilise. From the Ready screen, press SETUP. The display will show:
Press CAL. The display will now show:
Unplug the temperature probe and plug in the calibration plug marked "0°C". Press OK. The display will now show:
Plug in the calibration plug marked "25°C" and press OK. The display will now show:
Note that the calibration values shown above are typical - the actual values displayed will be different. The slope value shown should be between +9.0000E-03 and 1.1000E-02. The offset value should be between -1.0000E+00 and +1.0000E+00. If the values are outside this range press REJECT and try the calibration procedure again. If the values are within this range press ACCEPT. The values are stored in a non-volatile memory and are retained when the power is switched off. It is useful if a record is kept of the calibration values so that when the instrument is recalibrated the new values can be compared against the old.
Temperature Probe
The temperature probe is a Pt100 probe to DIN 43760 Class A with a temperature coefficient of resistance of 0.00385 W/W/°C. This tolerance class means that the probes are interchangeable without having to recalibrate the instrument. The temperature error at a nominal 25°C arising from swapping one probe for another is guaranteed to be less than 0.2°C. This has the advantage that the temperature probe itself does no need to be calibrated, only the electronics inside the instrument. To do this two precision resistance plugs are provided which have the same resistance as a Pt100 probe at 0 and 25°C respectively.
The actual resistances are 100.0W and 109.73W. Precision 0.1% tolerance resistors are used which means that the maximum temperature error arising from the resistance plugs will be less than 0.26°C. The maximum error which can arise from this calibration method is thus 0.2 + 0.26 = 0.46°C, well within the ASTM D5001 required accuracy of +/-1.0°C.
Humidity Sensor and Air Flow
These should be checked once per year using a test kit available from PCS Instruments or your distributor. This test kit measures the relative humidity and flow rate of the conditioned air system and determines if recalibration is necessary. Recalibration of the humidity sensor is accomplished by exchanging the sensor for a new factory calibrated unit. It is very unlikely that the air flow controllers will ever need recalibration but if they do they must be removed and returned to PCS Instruments.
Motor Speed
The motor speed is determined by counting pulses from the motor encoder with reference to the microcontroller hardware clock and does not require calibration. The speed can be checked using a suitable hand-held tachometer.
Test Duration
The test duration is measured by reference to the microcontroller hardware clock and does not require calibration. The test duration can be checked using a suitable stopwatch.
Software Version
The software version can be displayed by pressing INFO from the SETUP screen. The display will show:
*Note that the software version may be different.
PCS Instruments, 78 Stanley Gardens, London W3 7SZ, UK: Tribology Test Equipment: Traction Machines: Testing Fuels
Tel: +44 (0)20 8600 9920 
Fax: +44 (0)20 8600 9921 
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