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CAEN
Electronic Instrumentation
Voltage Temperature Compensation (VTC)
This option allows to adjust the output voltage, depending on the external temperature; it is available on
x8031 series only.
The external temperature can be measured independently for each channel, by connecting a PT1000
probe between PIN "T" and "GND" of connector AMP 280371-2 (DT8031 and R8031 on front panel, N8031
on rear panel; see p. 11).
On each channel, it is possible to set the Kt temperature coefficient and the Tstep compensation range.
As the compensation is enabled via the VTC parameter, Tref becomes equal to Text and the following
formula regulates the output:
Vout = Vset + Kt * Tstep * [(Text-Tref) / Tstep]
[square brackets indicate the integer part of the ratio]
Example:
Vset = 50V
Tstep = 0.2°C
Kt = 0.5V/°C
Tref = 25°C
If Text becomes 25.1° → Vout = 50V
If Text becomes 25.2°C → Vout = 50.1V
If Text becomes 25.3°C → Vout = 50.1V
If Text becomes 25.5°C → Vout = 50.2V
If Text becomes 25.6°C → Vout = 50.3V
If Text becomes 25.8°C → Vout = 50.4V
If Text becomes 25.9°C → Vout = 50.4V
If Text becomes 26°C → Vout = 50.5V
The compensation is signed, in fact if temperature decreases, voltage is reduced (If Text becomes 24° →
Vout = 49.5V)
By inverting Kt sign, if temperature increases, voltage is reduced, and vice-versa.
Notes:
If the probe is not installed, Text is considered >100°C; in this case no temperature compensation is
performed.
Compensation is guaranteed in the -40 to +100°C range.
Compensation does not modify Vset parameter, that remains as programmed initially. If, after the
compensation is done, the channel is turned off and then on, the voltage value returns to Vset (not
compensated).
If the PT1000 probe is disconnected, VTC is disabled and Vout returns to Vset.
Tref is updated when:
VTC is enabled;
Vset is updated with VTC enabled;
Kt is updated, for example:
Vset = 50V
Tstep = 0.2°C
Kt = 1V/°C
Tref = 25°C
Given Text monitored at 26°C, due to the compensation, the output voltage is updated to 51V. At this
point, if Kt is updated to 2V/°C, Tref is updated to 26°C (equal to Text) and Vout returns to 50V.
Kt: resolution 1mV/°C; maximum value +9.999V/°C; minimum value -9.999V/°C
Tstep: resolution 0.1°C; maximum value +2°C; minimum value +0.1°C
Tref e Text: resolution 0.1°C
803x Series 8-16 Ch. Programmable HV Power Supplies
23
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