STX Signal Transmitter Installation and Operation ... - Kistler-Morse

Chapter 8. MVS-STX Service Menu
AdjEx (adjust excitation)
AdjEx adjusts the STX PCB’s excitation
voltage output, which is used to excite the
sensors. AdjEx can range from 0 to 255,
corresponding to approximately 5 to 12.9 Volts.
The default, which varies slightly for each STX
PCB, is approximately 236. This corresponds
to the 12 Volts required by K-M silicon sensors
without Intrinsically Safe (IS) Barriers. Foil
gage sensors typically require 10 Volts of
excitation; refer to the manufacturer’s data
sheet for recommended excitation.
Note
If using IS Barriers, it may be necessary
to lower the excitation voltage.
Press the F2 and F3 Keys for coarse adjustment
or the Arrow Keys for fine adjustment of
AdjEx. Press the Enter Key to save the new
value in memory.
The value for excitation voltage output applies
only to the STX PCB for the current channel.
RstE2 (reset EEPROM)
This function resets most parameters (calibration,
filtering, tracking, STX PCB’s current
output, etc.) on the STX PCB for the current
channel to factory-set default values. RstE2
does not reset AdjEx or Iadj. Additionally,
RstE2 has no effect on parameters residing on
other PCBs, such as current outputs and
setpoints.
The display looks like this:
DEFAULT ADDR 12?
Yes
Addr 12 is the STX PCB’s hexadecimal
address — first rack (‘1’), second position in
rack (‘2’).
Press the F1 Key to default the STX PCB.
Press the F3 Key to exit without defaulting.
Res (resolution)
No
F1 F2 F3
This function controls effective resolution by
changing the conversion rate of the 21-bit
A/D converter. In general, the higher the
resolution, the slower the STX conversion time
(and time to switch monitoring
channels), but the greater the stability.
Table 8-1 shows the effective resolution
and associated conversion times.
You can select from 16 bt, 17 bt, 18 bt,
19 bt, 20 bt, and 21 bt. The default is 20 bt.
The value for resolution applies only to the
STX PCB for the current channel.
Effective Resolution Conversion Time
(bits)
(mS)
16 25
17 50
18 83
19 125
20 250
21 512
Table 8-1. Effective Resolution
Gain
Adjusting the gain increases or decreases
system sensitivity. The type of sensors
connected to the STX determines the required
gain. For example, for a nominal excitation
output of 12 volts, the reference voltage is one
quarter of the excitation voltage, or 3 volts.
At a gain of 1, the A/D converter spreads
2,097,152 counts over a range of ± 3 volts.
A gain of 2 spreads the counts over a range
of ± 1.5 volts, doubling the sensitivity. A gain
of 4 spreads the counts over a range of ± 0.75
volts, doubling the sensitivity again, etc.
The default setting is 2, appropriate for
K-M Microcell and L-Cell sensors. A gain
of 4 is appropriate for K-M Load Disc II,
Load Stand II, and Load Link I and II sensors.
See Table 8-2 for the available gain settings
and corresponding sensor input voltages.
The value for Gain applies only to the
STX PCB for the current channel.
Gain Sensor Input Voltage
2 ±1.5
1 ±3.0
4 ±0.75
8 ±0.375
16 ±0.1875
32 ±0.09375
64 ±0.046875
128 ±0.0234375
Table 8-2. Amplifier Gain
Digt (active digits)
This function sets the number of active digits
for input values. Note that active digits do not
include fixed zeros (refer to Form in Chapter
5, MVS-STX Display Menu). You can select
from 4, 5, and 6. The default is 5.
The value for Digt applies only to the
STX PCB for the current channel.
8-3