PS081 datasheet(33/155 Pages) AMSCO

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3-10

PSØ81

3.4

Capacitor, Cycle Time, Averaging

3.4.1

Load Capacitor (Cload)

The load capacitor is an important part of the circuit and has direct influence on the quality of the

measurement and the temperature stability. Therefore, we recommend the following values and ma-

terials:

insert picture: Cload.gif

Cload can be calculated by = 0.7 x Rsg x Cload

≈ 100 µs – 150 µs

Recommended materials:

C0G*

for highest accuracy

CFCAP

good, but not as good as C0G

X7R

with some minor losses in temperature stability

Polyester

with some minor losses in temperature stability

We do not recommend the use of ZOG capacitors !

* C0G capacitor up to 100nF are available by Murata GRM31 series

** Multi layer ceramic capacitor from Taiyo Yuden

Note:

C0G capacitors are definitely the best choice for high end applications (e.g. 6000 divisions (or

higher) legal-for-trade scales). CFCAP are also a good choice for high end scales and legal-for-trade

scales. For consumer scales X7R are the first choice because of their low cost. But they introduce

additional gain drift at lower temperatures ( < +5 °C ).

For consumer applications also a lot of other capacitors are well suited (e.g. Polyester).

3.4.2

Cycle Time (cytime)

The cycle time is the time interval between subsequent discharge time measurements. It covers the

discharge time and the time to charge again Cload. Following figure illustrates this relation.

Figure 3.12 Cycle time

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PS081 Datasheet(PDF) 33 Page - ams AG