Knick P45000, User Manual

Page: 21 / 38

P45000
21
5 Dimensioning of the Load
When selecting the load R
M
, the resulting load voltage, operating mode (single operation/side by
side operation), the supply voltage and the ambient temperature of the P45000 are to be taken
into account. In general, the load may fall within a range from R
M
= 0 … 200 Ω at I
out
= ±50 mA or
R
M
= 0 … 133 Ω at I
out
= ±75 mA. Upper restrictions are due to the maximum load voltage
➜
Maximum Load, p. 21 . Lower restrictions may be dependent on the operating mode (single
operation/side by side operation), the supply voltage and the ambient temperature
➜
Minimum Load, p. 21 .
5.1 Maximum Load
The P45000 generates a load voltage with the output current dependent from the input voltage at the
load R
M
. The load is to be selected in such a way that, with the expected output current, a load voltage
in the range -10 … 10 V results. If the load is selected too large, a linear representation of the input
voltage to the output current is no longer guaranteed.
The following diagram depicts the maximum load R
M,max
depending on the input voltage up to the
measuring range full scale for T
amb
= -40 … 85 °C (-40 … 185 °F) and U
HE
= ±13.5 … ±26.4 V:
0
100
200
300
400
500
600
0 25 50 75 100 125 150
R
M
,m
ax
[Ω
]
Measuring range [%]
100% = nominal input voltage range U
in
5.2 Minimum Load
In principle, the minimum permissible load is R
M
= 0 Ω. Under certain conditions (high ambient
temperature, high supply voltage, high input signal), a load R
M
> 0 Ω is to be selected in order to avoid
excessive heating of the P45000. With a higher load, the temperature of the product decreases during
operation. This reduces the expected failure rate and increases the service life of the P45000. Therefore
a load R
M
>> 0 Ω should be selected if possible.