BRUEL & KJAER 2694A, Руководство пользователя

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CHAPTER 4
The Use of Control Software BZ 5291
19
Fig.4.1 A transducer voltage overload occurs when the voltage input signal to the
conditioning amplifier exceeds the lower and upper voltage limits
Transducer voltage overload can occur if:
l
Excitation level too large – reduce the level if possible or use a transducer with
lower sensitivity.
l
For certain DeltaTron transducers, temperature variations can result in changes in
the DC bias voltage so that the upper or lower head-room is reduced. Large tem-
perature variations can therefore result in lower than normal excitation levels –
reduce the level if possible or use a transducer with lower sensitivity.
l
Missing transducer – check that a transducer is fitted and that the cable is properly
connected.
l
Short circuit or broken cable – check that the cable and the transducer are intact
and that all connections are good.
Note: The transducer voltage overload does not show which of the overload types
above caused the overload.
Transducer Current Overload : Another type of overload not detected by Condition-
ing Amplifier Type 2694 is the transducer current overload. This occurs when exces-
sive drive current is required, based on the cable length and the selected drive
current. This type of overload can occur with all types of transducers such as Delta-
Tron, IEPE, etc. The extent of a current overload depends only on the cable length,
its electrical characteristics and the current supplied to the transducer.
If a transducer current overload is suspected, the following options remove the over-
load condition:
l
Reduce the signal input level
l
Select a transducer with a lower sensitivity (less voltage output means less current
requirement)
Table 4.3
Overload types and
display messages in
prioritised order
Overload Type
Display
Message on PC
Display
Message on
Types
2694 A, C, D
Display
Message on
Type 2694 B
Transducer
Voltage Over-
load
tran V
Red and Green
LEDs
None – Not
Supported
Internal Signal
Overload
Signal Red LED Red LED
20.5 V
2 V
Set by
conditioning
amplifier
DC bias
voltage set by
transducer,
typically 12 V
without TEDS,
13 V with TEDS
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BE164411.book Page 19 Friday, May 18, 2001 11:51 AM