Thyracont VSH82, Operating Instructions Manual, Page: 42 / 52

42
vsh82-de-110318
4.6 Mode Hot Cathode
For certain vacuum processes it may be favoured to suppress the start of the hot
cathode sensor, which is automatically controlled by the transducer electronics.
Therefore it is possible to disable the hot cathode by software command via
RS485 interface:
"0":
Mode " disabled " hot cathode sensor remains switched-off
"1": Modus " enabled " start of hot cathode is automatically controlled by
the transducer (standard)
When the hot cathode is disabled your VSH82 behaves like a Pirani transducer
with range 1000 – 1x10
-4
mbar. Correspondingly the output "ur" in this case
means that actual pressure is below 1x10
-4
mbar.
With disabled hot cathode it is not possible to start the degas function (see
chapter 4.3).
Parameter "Mode Hot Cathode" is only temporarily saved in
the transducer memory. After mains supply is switched off or
disconnected the VSH82 will always be in mode "Hot cathode
enabled" !
Address Code Data cks CR
Address:
3 Bytes, decimal; address space RS485: 001 – 999
Code: "I" for reading, "i" for writing the parameter
Data: 1 Byte; "1" to enable, "0" to disable the hot cathode sensor
cks: 1 Byte, checksum, defined as sum over all Bytes of the fields
address, code and data, modulo 64 plus 64.
CR: Carriage Return (0Dh, 13d)
Example (for address-switch in position "1")
:
Action Telegram to
transducer Answer telegram
from transducer
Enable hot cathode
"001i1k
C
R
" "001i1k
C
R
"
Disable hot cathode
"001i0j
C
R
" "001i0j
C
R
"
Read mode hot cathode
"001IZ
C
R
" "001I1K
C
R
"
( enabled)
Please find further information about the Thyracont communication protocol in
chapter 4.2.