IntelliPack Series 841T Transmitter/Alarm User's Manual Frequency Input
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Transmitter/Alarm Field Programming Procedure…continued
9. Press the
“UP”
or
“DOWN”
push-button one time to cause
the module to auto-adjust its output level to the
corresponding full-scale output for the output range
selected. If the output is not exactly at the full-scale level,
then each successive depression
of the “UP” or “DOWN”
switch will increment or decrement the output signal by a
small amount. Holding the switch depressed will increase
the amount of increment or decrement.
10. Press the
“SET”
push-button to accept the full-scale value.
Note every ti
me “SET” is pressed, the yellow “Status” LED
will flash once and the full-scale output will be captured.
11. If configuring an 841T-0500 model which has no alarm
function, skip steps 12-17 and jump ahead to step 18.
12. Press the
“MODE”
push button one time until the yellow
zero/full-scale LED goes out and the yellow relay LED turns
ON (see Table 4). In this mode, the unit is ready to accept
an input setpoint level for the alarm. If you do not wish to
change the setpoint, skip to step 15.
13. Adjust input source to the High or Low alarm setpoint level.
14. Press the
“SET”
push button to accept the setpoint. Note
every time “SET” button is pressed, the yellow status LED
will flash once and the value at the input will be captured.
15. Press the
“MODE”
push button one time and the yellow
relay LED should start flashing (see Table 4). This means
the unit is ready to accept the dropout level for the alarm. If
you do not wish to change the dropout, skip to step 18.
16. Adjust the input frequency to the desired dropout level.
17. Press the
“SET”
push button to accept the input dropout
level. Note every time “SET” is pressed, the yellow status
LED will flash once and the value at the input will be
captured. The module will use the difference between the
setpoint and dropout values to calculate relative deadband.
18. Press the
“MODE”
push button one time to complete the
program sequence and return to run mode. The green
“RUN” LED will turn ON, the yellow “Zero/Full-Scale” LED
will be OFF, and the yellow alarm LED will be ON or OFF
according to the alarm status. The module will now assume
a transfer function based on the zero and full-scale values
just set. The setpoint and dropout of 841T-1500 units is
used to determine the alarm deadband. Note that until
“SET” is pressed, pushing “MODE” will only toggle between
the zero & full-scale, plus setpoint & dropout adjustment
modes (841T-1500 units), without affecting their values.
Further, if no push-buttons are depressed for a period
greater than 2 minutes, then the module will automatically
revert to run mode (green “Run” LED will light) and no
changes will be made to the original zero, full-scale, and
optional setpoint & dropout settings.
Notes (Field Program Procedure):
1. In field configuration mode, the yellow zero/full-scale LED
(Z/FS) and relay LED (RLY) are used to indicate which
program parameter is being adjusted as illustrated in Table 3:
Table 3: Field Configuration LED Program Indication
LED INDICATOR
Constant ON
FLASHING
Yellow Zero/Full-Scale
(labeled “Z/FS”)
Zero
Full-Scale
841T-1500 Only
Yellow Relay
(labeled “RLY”),
High or Low
Setpoint
High or Low
Dropout
Notes (Field Program Procedure)…continued:
2. To summarize, the green “Run” LED is turned off in field
configuration mode. The yellow zero/full-scale LED is ON or
FLASHING when the corresponding zero or full-scale value is
being set in field configuration mode and turned OFF in run
mode. The yellow alarm LED is ON or FLASHING when the
corresponding setpoint or dropout/deadband level is being set
in field configuration mode.
3. If the transmitter/alarm is in field configuration mode and no
push buttons are pressed after 2 minutes, then the module
will return to the run mode, the green “Run” LED will light, and
no changes to any program parameters will be made.
4. Latching alarms require a push button reset to exit the alarm
state (this may also be accomplished under software control).
Use the up or down push-button on the front of the module to
reset a latched alarm relay.
4.0 THEORY OF OPERATION
Refer to the Block Diagram of Drawing 4501-682 and
4501-692 to gain a better understanding of the circuit. Note that
these transmitters use a comparator and logic gate to convert the
input signal into a digital pulse stream. The comparator is used
to provide the threshold and hysteresis, while the logic gate is
used to “square” the waveshape. The microcontroller samples
the input pulse stream while tracking the number of internal
sampling clock cycles to determine the period of the input signal
and derive its frequency. The sampling clock rate is 666666.667
cycles per second, or 1.5us per cycle. For frequencies below
100Hz, the number of sampling clock cycles in one input wave
cycle is used to determine the period of the input. For
frequencies in the range of 100Hz to 1000Hz, the number of
sampling clock cycles in eight input wave cycles is used to
determine the input period. As such, internal resolution
decreases with increasing frequency and is generally better than
the display resolution for the range, except near the upper end of
the 100Hz and 1000Hz ranges, where it approaches half the
display resolution for these ranges. For the 50KHz range, the
number of input wave cycles in a gated 1 second period is used
to calculate the input period. The microcontroller will compute
the input frequency and complete the transfer equation according
to the transmitter type and its embedded function. It sends a
corresponding output signal to an optically isolated Digital-to-
Analog Converter (DAC). The DAC then updates its current or
voltage outputs in response. The microcontroller also compares
the signal value to the limit value and completes all necessary
alarm functions per its embedded program (841T-1500 units
only). The embedded configuration and calibration parameters
are stored in non-volatile memory integrated within the
microcontroller. Only the functions required by an application are
actually stored in memory
—new functionality can be downloaded
via the IntelliPack Configuration Program and Serial Port Adapter.
A wide input switching regulator (isolated flyback mode) provides
is5V and +16V power to the circuit, plus an is15V
output circuit supply.