RC Systems ST-72, Instruction Manual, Page: 36 / 142

ST-72 User's Manual
Document: UM-1007 Revision Level A
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out values described in section 2.4.6.2 . This menu entry is determined by the A/D
converter resolution of the channel’s input. For example, if the input is a 10 bit
Modbus® device with zero at 200 counts and 100% at 1000 counts, then this menu’s
MIN should be set at 200 and MAX at 1000. If communicating with the ST-72’s optional
12 bit Analog Input PCB the MIN should be 800 and the MAX 4000.
If the input device’s resolution is unknown, the live counts variable on the Combination
screen displays actual raw A/D counts currently being read by this channel. This reading
may be used to test the input device for what A/D counts are provided for zero and
100% if these values are unknown. Forcing the input device to read zero should provide
the A/D counts value needed to make this channel’s display also read zero. Likewise,
forcing the input device to read 100% should provide the A/D counts value needed to
make the ST-72 channel’s display also read 100%.
Note: Each Data From : item has a matching default Min/Max counts value of 20% to
100% with ± 5% over/under range applied. If the default value is incorrect for the input
device it should be edited.
2.4.4.3 FILTER SAMPLE COUNT
The FILTER SAMPLE COUNT is the number of samples from an Analog Input
channel that are averaged together before displayed. The valid range is 1-40 with the
default value of 10. If a channel has a noisy input the sample rate can be increased
causing the noise to average itself out. This higher number of samples causes the
channel to react slower to input.
2.4.4.4 LOCAL CAL
LOCAL CAL is available with the Analog Input option. There are three choices Board
Default, On, and Off . With the Analog Input option used for both the Analog and Bridge
input boards, Board Default automatically turns the local calibration feature On for the
Bridge input and Off for the Analog Input. If there is a need to calibrate a channel locally
and the board default is Off it can be manually changed.
ST-72 CAL MODE features allow pushbutton calibration of zero and span values. This
feature should be utilized only when there are no other zero/span controls within the
monitoring system since it is inappropriate to calibrate a signal at more than one point.
Therefore, if calibration is to be performed at another transmitter or monitoring device,
the ST-72 CAL MODE feature should not be used.
The CALIBRATION MENU allows entering the correct
Cal ZERO
&
Cal SPAN
set-point
values needed to calibrate the sensor. These are entered in the same engineering units
as input range.
Set Zero & Set Span
controls in this menu allow pushbutton
calibration by moving the highlight bar to each and pressing the
Edit
. A live reading of
the channel’s value in the tool tip box allows calibration checks to see if an adjustment is
needed. Unintentional calibrations are reset by the
Set Unity Gain
menu item.
Set