16-channel Conditioning Amplifier Type 2694 –
User Manual
18
A-, B-, C-, D-Weighting
: The internationally standardised filter characteristics for
measuring sound. The filters comply with IEC 651 Type 0. Whenever one of these
filters is selected, the
and
parameter fields disappear, and the fixed
high- and low-pass filters are automatically set to 0.1 Hz and 50 kHz respectively.
Low-pass Filters
:The low-pass filter is set at the factory to 50 kHz, –1 dB point (20 dB/decade). If
other, low-pass filters are required, then these can be ordered as optional filters.
Output Sensitivity
For setting the output sensitivity in calibrated 10 dB steps, you can select the values
in Table 4.2. These values are based on a ‘neutral’ transducer sensitivity of 1 V/ms
–2
for DeltaTron inputs.
Note:
The output sensitivity can also be set from the Peak Meter menu.
Table 4.2
Output sensitivity values for DeltaTron input and associated gain factors in Type
2694 instruments
Overload Indications
Type 2694 amplifiers have overload detection facilities to ensure that your measure-
ments are valid. The overload conditions listed in Table 4.3 are indicated by the red
LEDs on the front panel for the respective channels. The LEDs indicate instantane-
ous overload conditions. Alternatively, the overload information can be obtained via
the RS–232 interface. An overload is indicated in the control software by a black
triangle. A complete overloads log is available in the View Message Log window.
The overload indications disappear when the overload condition is remedied. Re-
gardless of the duration of the overload, a lighted LED is always displayed for a
period that allows it to be seen.
See Table 4.3.
Transducer Voltage Overload:
The transducer voltage overload is only used for
DeltaTron inputs. The CCLD (Constant Current Line Drive) supplies a constant cur-
rent that is converted into a fixed DC bias voltage in the DeltaTron accelerometer.
The voltage signal swings around the nominal 12 V DC bias voltage and must be
within the lower and upper voltage limits of 2 V and 20.5 V (respectively) set by the
conditioning amplifier (see Fig.4.1).
DeltaTron
Total gain in
2694 A, C, D
Total gain in
2694 B
316 mV/V
1 V/V
3.16 V/V
10 V/V
31.6 V/V
100 V/V
–10 dB
0 dB
10 dB
20 dB
30 dB
40 dB
0 dB
20 dB
Hz
kHz
kHz
BE164411.book Page 18 Friday, May 18, 2001 11:51 AM
