Ohmic instruments DPX-200 User manual

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DPX-200 MANUAL
DEW POINT TRANSMITTER
SF-SLS-554 (A)
Phone [phone]
Toll Free(800) 626-7713
Fax [phone]
www.ohmicinstruments.com
Sales: [e-mail]
Service: [e-mail]
Ohmic Instruments
3081 Elm Point Industrial Drive
St. Charles, MO 63301 USA

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© Ohmic Instruments
2014
All rights reserved. This manual may not be reproduced in complete form
without written permission of Ohmic Instruments . Information contained
in this manual is believed to be accurate and reliable; however, no
responsibility is assumed by Ohmic Instruments for its use. Ohmic
reserves the right to supply its instruments with design changes and/or
component substitutions that may not be documented in this manual.

3
INTRODUCTION
The DPX-200 is a microprocessor-based dew point transmit-
ter used to monitor the output air from dryer systems as well
as ambient conditions. The DPX-200 determines the dew
point temperature from the measurements of water vapor
and dry bulb temperature of the air sample. These dew point
calculations are fully compensated for variations in sample
dry bulb temperature using preprogrammed Psychrometric
equations.

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1. Make connections to output
terminals located inside the unit
as labeled to their function (see
the above illustration). The
transmitter operates as a 4-wire
device. DO NOT TIE THE (-)
POWER CONNECTION TO
THE (-) SIGNAL OUTPUT ON
THE TRANSMITTER. THIS
WILL DAMAGE THE UNIT. For
analog output values refer to
the table on Page 9.
1. + Power (18-28 VDC) 3. +Vout (0-5 volts) 5. +mA (4-20mA)
2. - Power 4. -Vout 6. -mA
Calibration Lockout
(do not remove)
°F / °C jumper shown
in °F position
OPERATION

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2. When installing the remote
probe in pipelines or vessels,
disconnect the probe from the
transmitter to prevent breaking
wires in the probe assembly.
Reconnect the probe to the
transmitter after the probe is
installed. *The probes are
not interchangeable as
each probe has its cali-
bration data stored in an
EEPROM on the trans-
mitter.
3. Connect the transmitter to a 18
to 28 volt DC power supply and
turn power on.
4. Wait for the dew point reading
to stabilize. The transmitter
range is limited by the response
of the internal sensor. There is
no over/under range indica-
tion, and the accuracy is not
rated beyond -40°F to +80°F
(-40°C to +20°C).
RECALIBRATION
The DPX-200 is a microprocessor
based-instrument and has no user
adjustments. *The probes are
not interchangeable as
each probe has its calibra-
tion data stored in an
EEPROM on the transmitter.
The system can be recertified to
NIST traceable standards by return-
ing it to Ohmic Instruments Co.
Recertification is recommended on
a yearly basis.
OPTIONAL RS-232 INTERFACE–
Connecting the DPX-200 to Your
Computer
Connecting to a serial port If your
DPX-200 includes the optional RS-
232 adapter cable, it can be con-
nected to your computer’s 9-pin PC
serial (COM) port. If your computer
has a 25-pin COM port, 25-pin to 9-
pin serial adapters are available from
most computer stores and can be
used with the adapter cable [Serial
data is transmitted using Pin 5
(ground), Pin 3 (transmit), and Pin 2
(receive)]. Some computer COM
ports and serial adapters are not fully
implemented (not all pins are used).
If the DPX-200 is connected to a
partially implemented serial port,
functions may be erratic or the unit
may fail to communicate. Consult the
owner’s manual for your computer if
this occurs. Set up your communica-
tions program as described on Page
6.
Connecting to a USB port If your
DPX-200 includes the optional RS-
232 adapter cable, it can be con-
nected to your computer’s USB port
via an optional RS-232 to USB
adapter from Ohmic. Ohmic recom-
mends using an RS-232 to USB
adapter only with Windows XP© and
later versions. Connect the DPX-200
using the RS-232 adapter and RS-
232 to USB adapter. Turn on your
computer. When your computer rec-
ognizes the device click OK and fol-
low the instructions for installing the
driver software. Set up your commu-
nications program as described on
Page 6.

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Communications Programs
The DPX-200 transmits data via its
RS-232 output as soon as it is pow-
ered up. In order to receive the da-
ta, a communications (or terminal)
program must be running on your
computer. We recommend Tera
Term; it is easy to use, free, and
available for download from
www.download.cnet.com. When you
reach that page, type “Tera Term” in
the Search box; you will then be able
to download the installation program.
Then:
1. Install the program and run it.
2. A New Connection window will
open. Click the “Serial” button,
then select the COM port you
will be using, and click OK.
3. Tera Term should now ready to
receive data from the DPX-200.
Make sure they are connected
via the adapter cable, and pow-
er up the DPX-200.
4. Introductory text will be dis-
played indicating the version of
the embedded program. The
computer will then display three
numbers: Relative Humidity,
Dry Bulb Temperature, and
Dew Point. New readings will
be displayed every few seconds
and are in a comma delimited
format that can be copied and
pasted into a spreadsheet pro-
gram, if desired.
If readings are not displayed, turn
the DPX-200 off, and in Tera Term
click on Setup in the menu bar, then
select Serial Port. This will open a
window where you can check sev-
eral parameters:
 Port: Try another port until you
find the right one.
 Baud rate: Should be 9600.
 Data: 8 bit
 Parity: None
 Stop: 1 bit
 Flow Control: Off
Once you get a working display you
may want to save your settings.
Refer to Tera Term’s help file for
information on this and other func-
tions.
Other communications programs
can also be used; some older ver-
sions of Windows include one
called HyperTerminal. Refer to its
help file for information on using it
and applying the parameters above.

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Particulate Contamination: The sen-
sors should be shielded from partic-
ulate contaminants.
Chemical Contamination: The sen-
sors should not be exposed to corro-
sive or reactive chemicals.
Fahrenheit / Celsius
The DPX-200 can be user-
configured to display either Fahren-
heit or Celsius readings on the
computer. Simply move the jumper
shown on Page 4 to the position for
the desired readings. Please note
that whenever this jumper is
moved, the setting will not be imple-
mented until the unit is reset by re-
moving power and then reapplying
it. Be careful not to remove the
jumper marked on Page 4 as Cali-
bration Lockout. This jumper keeps
the calibration points locked in; re-
moving it can cause the DPX-200 to
lose calibration.
Communications Commands
Commands can be typed in upper
or lower case characters (older
DPX-200’s require commands to be
typed in upper case only).
Cn<Enter>Set auto data transmit
interval for displayed
readings to n seconds
(n is a number from 0
to 32767). For n=0, 1,
and 2, automatic trans-
mission is turned off.
Default value is n=3
seconds.
Note: To enable the screen to dis-
play what you are typing, go to the
menu bar in Tera Term, click on
Setup, select Terminal, and
checkmark the “Local Echo” box.
SENSOR PRECAUTIONS
Under normal operating conditions,
the sensors used by the DPX-200
will maintain calibration specifica-
tions for over five years of continu-
ous use, assuming that the precau-
tions outlined below have been fol-
lowed. However, if used in plastics
drying operations, hydrocarbons
from the out gas of the plastic resin
dryer might condense over time on
the sensor. Eventually the sensor
will have to be replaced. To main-
tain NIST traceable certification, the
unit should be returned to Ohmic
Instruments Co. for sensor replace-
ment. Ohmic requires that a filter be
used to prevent contaminants from
damaging the sensor. The following
is a list of limits of operation. Ex-
ceeding these limits can cause sen-
sor failure and voids all warranties.
Humidity:
Temperature:
Max. Pressure:
Excitation:
0 to 100% RH - NON CONDENSING
0 to 185°F
175 psig
The sensor current is not to exceed 50µA
Limits of Operation

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SPECIFICATIONS
Water Vapor Sensor:
Temperature Sensor:
Dew Point Range:
Calibrated Range:
Accuracy:
Dry Bulb Range:
Dry Bulb Accuracy:
Operating Temperature:
Maximum Pressure:
Sensor Response Time:
Analog Output (4 wire Dew Point):
Microprocessor:
Power:
Fuse:
Optional Computer Interface:
Communication Setup:
HC-610
10K NTC Thermistor
-45° to +90°F
-40° to +80°F
±4°F from -40° to +20°F
±2°F from +20° to +80°F
0-200°F
±1°F
Probe: 0 to 185°F
Electronics: +40° to +120°F
175 psig for remote probe
10 sec. for 63% step
0 to 5 volts DC
4 to 20mA
Philips 80C552
18 to 28 VDC
½ Amp, 250V
Bi-directional RS-232. ASCII, Com-
ma Delimited Format
9600 Baud Rate, 8 Data Bits, 1
Stop Bit, No Parity, Flow Control off
If you need additional help for your particular application, contact:
OHMIC INSTRUMENTS
410-820-5111

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DPX-200 Analog Output Table Centigrade/Fahrenheit
F/C-DP V out mA F/C-DP V out mA F/C-DP V out mA F/C-DP V out mA
-40 0.000 4.000 -91.292 8.133 22 2.583 12.267 50 3.750 16.000 -39 0.042 4.133 -81.333 8.267 23 2.625 12.400 51 3.792 16.133 -38 0.083 4.267 -71.375 8.400 24 2.667 12.533 52 3.833 16.267 -37 0.125 4.400 -61.417 8.533 25 2.708 12.667 53 3.875 16.400 -36 0.167 4.533 -51.458 8.667 26 2.750 12.800 54 3.917 16.533 -35 0.208 4.667 -41.500 8.800 27 2.792 12.933 55 3.958 16.667 -34 0.250 4.800 -31.542 8.933 28 2.833 13.067 56 4.000 16.800 -33 0.292 4.933 -21.583 9.067 29 2.875 13.200 57 4.042 16.933 -32 0.333 5.067 -11.625 9.200 30 2.917 13.333 58 4.083 17.067 -31 0.375 5.200 01.667 9.333 The DPX is NOT rated above 59 4.125 17.200 -30 0.417 5.333 11.708 9.467 this point for centigrade 60 4.167 17.333 -29 0.458 5.467 21.750 9.600 measurements 61 4.208 17.467 -28 0.500 5.600 31.792 9.733 31 2.958 13.467 62 4.250 17.600 -27 0.542 5.733 41.833 9.867 32 3.000 13.600 63 4.292 17.733 -26 0.583 5.867 51.875 10.000 33 3.042 13.733 64 4.333 17.867 -25 0.625 6.000 61.917 10.133 34 3.083 13.867 65 4.375 18.000 -24 0.667 6.133 71.958 10.267 35 3.125 14.000 66 4.417 18.133 -23 0.708 6.267 82.000 10.400 36 3.167 14.133 67 4.458 18.267 -22 0.750 6.400 92.042 10.533 37 3.208 14.267 68 4.500 18.400 -21 0.792 6.533 10 2.083 10.667 38 3.250 14.400 69 4.542 18.533 -20 0.833 6.667 11 2.125 10.800 39 3.292 14.533 70 4.583 18.667 -19 0.875 6.800 12 2.167 10.933 40 3.333 14.667 71 4.625 18.800 -18 0.917 6.933 13 2.208 11.067 41 3.375 14.800 72 4.667 18.933 -17 0.958 7.067 14 2.250 11.200 42 3.417 14.933 73 4.708 19.067 -16 1.000 7.200 15 2.292 11.333 43 3.458 15.067 74 4.750 19.200 -15 1.042 7.333 16 2.333 11.467 44 3.500 15.200 75 4.792 19.333 -14 1.083 7.467 17 2.375 11.600 45 3.542 15.333 76 4.833 19.467 -13 1.125 7.600 18 2.417 11.733 46 3.583 15.467 77 4.875 19.600 -12 1.167 7.733 19 2.458 11.867 47 3.625 15.600 78 4.917 19.733 -11 1.208 7.867 20 2.500 12.000 48 3.667 15.733 79 4.958 19.867 -10 1.250 8.000 21 2.542 12.133 49 3.708 15.867 80 5.000 20.000

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WARRANTY
Not withstanding any provision of any agreement the
following warranty is exclusive.
Ohmic Instruments warrants each instrument it
manufactures to be free from defects in material and
workmanship under normal use and service for the
period of 1-year from date of purchase. This warranty
extends only to the original purchaser. This warranty
shall not apply to fuses or any product or parts which
have been subjected to misuse, neglect, accident, or
abnormal conditions of operation.
In the event of failure of a product covered by this
warranty, Ohmic Instruments will repair and recali-
brate an instrument returned within 1 year of the
original purchase: provided the warrantor's examina-
tion discloses to its satisfaction that the product was
defective. The warrantor may, at its option, replace
the product in lieu of repair. With regard to any instru-
ment returned within 1 year of the original purchase,
said repairs or replacement will be made without
charge. If the failure has been caused by misuse,
neglect, accident, or abnormal conditions of opera-
tions, repairs will be billed at a nominal cost. In such
case, an estimate will be submitted before work is
started, if requested.
THE FOREGOING WARRANTY IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY IMPLIED
WARRANTY OF MERCHANTABILITY, FITNESS,
OR ADEQUACY FOR ANY PARTICULAR PUR-
POSE OR USE. OHMIC INSTRUMENTS SHALL
NOT BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES, WHETHER IN
CONTRACT, TORT, OR OTHERWISE.
If any failure occurs, the following steps should
be taken:
1. Notify Ohmic Instruments giving full details of the
difficulty, and include the model, type, and serial
numbers (where applicable). On receipt of this
information, service data, or shipping instructions
will be forwarded to you.
2. On receipt of shipping instructions, forward the
instrument, transportation prepaid. Repairs will be
made and the instrument returned, transportation
prepaid.
SHIPPING TO MANUFACTURER FOR REPAIR
OR ADJUSTMENT
All shipments of Ohmic Instruments products should
be made via United Parcel Service or "Best Way"
prepaid. The instrument should be shipped in the
original packing carton, or if it is not available, use
any suitable container that is rigid and of adequate
size. If a substitute container is used, the instrument
should be wrapped in paper and surrounded with at
least four inches of excelsior or similar shock absorb-
ing material.
CLAIM FOR DAMAGE IN SHIPMENT TO
ORIGINAL PURCHASER
The instrument should be thoroughly inspected
immediately upon delivery to purchaser. All material
in the shipping container should be checked against
the enclosed packing list. The manufacturer will not
be responsible for shortages against the packing
sheet unless notified immediately. If the instrument is
damaged in any way, a claim should be filed with the
carrier immediately. (To obtain a quotation to repair
shipment damage, contact Ohmic Instruments.) Final
claim and negotiations with the carrier must be com-
pleted by the customer.
Ohmic Instruments will be pleased to answer all
application or use questions, which will enhance your
use of this instrument. Please address your requests
or correspondence to:
Ohmic Instruments
3081 Elm Point Industrial Drive
St. Charles, MO 63301 USA
ATTN: Technical Support
Or call Ohmic Technical Support at 410-820-5111.
All rights reserved. This manual may not be repro-
duced in full or in part without written permission of
Ohmic Instruments. Information contained within this
manual is believed to be accurate and reliable.
However, Ohmic Instruments assumes no liability for
its use. Ohmic Instruments reserves the right to
supply its instruments with design changes and/or
component substitutions that may not be document-
ed in this manual. Contact our engineering depart-
ment for information on equipment revisions not
covered in this manual.
Phone [phone]
Toll Free(800) 626-7713
Fax [phone]
www.ohmicinstruments.com
Sales: [e-mail]
Service: [e-mail]

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