PS081 datasheet(54/155 Pages) AMSCO

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3-31

PSØ81

Figure 3.30 Rp placement

There are several criteria to decide whether a parallel resistor (Rp) should be used or not. Please

find a detailed description in our dedicated Whitepaper WP002. Recommendations of whether the

use of Rp is recommended or not and the size of it is automatically calculated by an Excel-Sheet

available from acam. If it is recommended to add an Rp resistor it can be an ordinary fixed resistor

with no special requirements.

3.6.5

Gain-Drift of PSØ81 itself – Optimization with Mult_PP

The PSØ81 has a very low gain drift of ~ 1ppm/K in case the Mult_PP factor is set properly. The

reason for this gain drift is different than in an A/D-Converter. Because of this, we give some back-

ground information in this section to understand the cause of the gain drift of PSØ81 and also we

give some hints how to measure it properly.

Background: In a classical A/D converter application the temperature drift of the resistors of the

operational amplifier have to match very exactly. A mismatch is seen as gain drift. In PSØ81 the phy-

sical reasons are totally different. PSØ81 has a TD-Converter with no preamplifier.

The gain drift of the PS081 electronics comes mainly from the delay time of the comparator. In

Wheatstone mode the analog multiplexer is part of this delay time and therefore the selected type of

the analog multiplexer affects this value. When setting pptemp = 1 in register 2 the PS081 can mea-

sure the delay by means of the two resistors at ports PSEP1 and PSEP2. The determined correction

factor can be adjusted by factor Mult_PP

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PS081 Datasheet(PDF) 54 Page - ams AG