Model2000 Series
DewPrime
Dew Point Hygrometers
-----------
Operating
Instructions
3.5 FUNCTIONS OF
FRONT PANEL
INDICATORS
The CONTROL indicator
represents
the current that
is
controlling the heating or
cooling
of the Sensor.
All
lights on
represents
high
cooling
current; no lights
on
represents high heating
current.
During normal
operation.
the number
ofbars
lit will
be
roughly indicative of the dew point. For a low
dew
point
,
more cooling current
will
have to be
supplied
continually, so more bars
will
be lit (6 - 8 bars). At
high
dew points, little current may be used so that five
or
fewer lights will be on.If the system needs to servo
to
maintain the dew point, one or more bars may
tempo-
rarily
illuminate.
During the
begjm;ng
(heating)
phase of an
ABC,
the
CONTROL bars
first
indicate
the imbalance caused
by
entering the ABC mode by having 0 or
1
bar lit. Then. as
the Sensor dries out, the
indicator
should move
toward
the
center
(
4-6
bars).
If
it
does not, then an
intemai
balance adjustment must be made (see subsection
5.6.1).
The adjustment is made using the bar display.At the
end
of a
successful
balance cycle, all bargraph LEDs
will
ilbnninate.indicating
a heavy cooling current, and
then
stabilize as the dew point is
found.
The
ALARM
LEDs are on when an alarm condition
is
satisfied. In a Latch
mode
,
if
a satisfied
a1arm
condition
becomes
unsatisfied
,
the LED
begins
to
flash,
indicating
that there was an
alann
condition.
Depressing
the
RSET
key turns off the flashing
LED.If
a
satisfied
alann
condition
exist
s when an ABC is started, the almm
is
cancelled, but the LED
flashes
.
If
an
alarm LED
is
flashing when an ABC is
started,
the flashing will be
cancelled.
NOTE
The alann relays are never
energized
during an ABC
cycle.
The ABC LED comes on when an ABC cycle
starts,
whether amomatic or
manual.It
remains on
steady
durin
g
the heat phase and the balance
phase.
After
a
successful
balance,the
ABC LED flashes for
the
duration
of the ABC hold time.
IfHold
is on, the
analog
outputs are held until the LED
is out.
The
CONTAMINA'IED
LED comes on
i
f
an ABC
is
unsuccessful
After the heat phase of an ABC, attempt
to
:find
an
acceptable
balance point.
If
the
mirror is
badly
contaminated
and balance is
impossible
,
then the LED
indictaes
a
need to clean the Sensor
mirror.
3.6
R.S-232
SERIAL
PORT
The Model 2000 Series serial port on the rear panel can
be
used
to operate the unit,
program
parameters,
or
output data to a printer, data
terminal,
or
personal
computer. To be
effective
,
the
RS-23
2
must be
con-
nected to a computer
equipped
with an
appropriate
communication
software. At the factory, we
use
PROCOMM
and
PROCOMM+.
3.6.1
Computer Connection
Connect an RS-232 cable between the Model
2000
Series 25-pin D-Type
connector
and the RS-232
serial
port of a PC, terminal, or
printer
.
All
handshaking
lines
are available at the connector;
however
a 3-wire
XON/
XOFF cable is all
th.al:
i
s
nOimally
required. The serial
port is wired as a DTE device (Data
Temrinal
Equip-
ment); i.e.,
Transmit
(TxD) is pin 3 and Receive
(RxD)
i
s
pin 2. For
connection
to a DCE device (Data
Commu-
nications
Equipment)
such as a PC, a direct
pin-to-pin
cable is
necessary.For connection
to another DTE
device
such as
a
printer, a null modem
is
required.
3.6.2 'PC
Setup
Set
the
Model 2000 Series to the preferred baud rate
via
the
:front
panel
The
available
baud rates are 19.2K.,
9600,4800,2400,
1200, and
300.
Set up the
PC's
communication
program for a baud
rate
to match the
Model2000.The protocol
should
be
8
data
bits,
1
stop bit, and no parity
(N81
).
Once
communication is established,
the
available
commands can be viewed by
accessing
the HELP
menu.
Press the
ENTER
key on the
computer keyboard.
Enter Command
(H
for
Help): Type the letter ''H"
and
press
ENTER.
The HELP menu
shovvn.
in Table 3-3 will be
displayed
on the
computer's
screen.
NOTE:If
no actions
are
taken, the Model 2000 Series will revert to data mode
in
15
seconds.
3-5
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