EDI CTT-2 Manuale operativo - Pagina 5

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9.4

Impedance calibration.

There are three calibration factors involved in calibration. They are the short circuit,

the the offset, and the reference resistor factors. The values in use can be read by

typing 'Cz'. The reference resistor 'Cr' value should not be changed unless the unit

has been repaired. The calibration starts with a short circuit then a resistance test.

The 'Cs' is adjusted for 0 ohms, and the 'Co' is adjusted for correct reading of a 5K

resistor. There is interaction between the 'Cs' and 'Co' values, so the calibration may

need to be repeated a few times for the best balance between short circuit and high

impedance readings.

9.5

Short circuit calibration.

9.5.1

9.5.2

9.6

5100 ohm calibration point

9.6.1

9.6.2

9.7

Storing the new calibration values is done by typing 'Cm1234'. If 'Cm' is entered

with any other value, you will get an error message and the values will not be

stored.

CTT-2 Manual V1.01

Set the offset to 1 by typing "Co1'.

Place a short across the transducer connector. Type 'f100000'. The returned

impedance should be between 0 and 0.5 ohms. If not, the 'Cs' value, nominally

2022, must be changed. If the impedance is greater than 0, increase the value of

Cs slightly and read the impedance. Keep adjusting the 'Cs' until the short reads

between 0 and 0.1 ohms. If the required 'Cs' value is less than 2000 or greater

than 2040 the CTT-2 may require repair.

Connect a 5100 ohm 1% resistor to the transducer connector. Type 'f100000',

the returned impedance should be 5100 +/- 250 ohms. If it is not, check the 'Co'

value. Increase 'Co' to lower the reading, decrease it to increase the reading. The

'Co' value must be between 1 and 6. If a 'Co' value over 6 is required, the CTT-2

should be returned to the factory for repair.

Check the readings with the 10 ohm and the 510 ohm resistor and repeat steps

9.5.2 through 9.6.2 until the results are within +/- 5% tolerance of the 10 ohm

and 510 ohm resistor values.