TDC-GP22 datasheet(74/93 Pages) AMSCO

74 / 93 page

TDC-GP22

acam messelectronic gmbh - Friedrich-List-Str.4 - 76297 Stutensee - Germany - www.acam.de

4-29

Three main parameters have to be considered, to select the correct gain factor:



base resistance of the temperature sensor (e.g. PT500, PT1000)



used Schmitt trigger (GP22-internal, external 74AHC14)



GP22 supply voltage

The appropriate gain correction factors are provided in table 4-3 (“Absolute gain vs. Vio”).

Import note:

The gain correction factors for the external Schmitt trigger exclusively refer to the

74AHC14 Schmitt trigger. Other types (e.g. 74HC14) require different gain factors, in

order to ensure a correct compensation. According to that, we strongly recommend to

use a 74AHC14 as external Schmitt trigger.

Example 1:

Application with PT1000 Sensor, GP22 internal Schmitt trigger and 3.0 V supply

voltage. According to table 4.3 a gain factor of 0.9931 has to be selected. The gain

corrected result is calculated then by the following equation:

Tcorr=Tuncorr/0.9931

Example 2:

Application with PT500 Sensor, external 74AHC14 Schmitt trigger and 3.6 V supply

voltage. Table 4-3 now specifies a gain factor of 0.9980. The gain corrected result is

calculated as follows:

Tcorr = Tuncorr/0.9980

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