Omega Engineering DP97 User manual

CONTENTS PAGE
1. INTRODUCTION 1
Full description of the DP97
Front Panel information at a glance
2. INSTALLATION 3
Supply Connection
Input connections –Sensors
3. OPERATION 4
i) To read sensor temperature directly
ii) To read differential temperature
iii) Matching DP97 to calibrated sensors
iv) Error indications
v) ¾ wire recognition
4. INSTRUMENT RE-CALIBRATION 6
5. ANALOGUE (RE-TRANSMISSION) OUTPUT 8
Connection and Operation
6. RS232 COMMUNICATIONS 9
Connection and Operation
Using RS232 interface for digital probe matching (corrections)
7. USE OF “CORRECTIONS PC SOFTWARE” 12
Information in this publication may be subject to change; the DP97 is a
microprocessor based, software driven instrument and may therefore be subject
to software and hardware changes in line with our policy of continuous product
development.

1. INTRODUCTION
A high precision portable thermometer for metrology and other exacting laboratory
applications, the DP97 is a proven instrument used world wide as a laboratory and site
standard in pharmaceuticals, medical, food, environmental testing, R & D, and general
industrial applications. It is particularly suitable as the reference standard for
temperature calibration baths.
The DP97 Digital Thermometer utilises highly advanced microprocessor circuit design to
achieve exceptional measuring accuracy, linearisation conformity and stability in a
versatile but easy to use configuration.
Based on a high resolution 20 Bit Analogue to Digital Converter, all measurement
computations are performed digitally without drift. The 5 digit LED display provides a
readout to 0.01°C over the entire –199.99 to +849.99°C range; alternatively °F, Kelvin or
Ohms values can be displayed up to 999.99 units.
Single or dual Pt100 3 or 4 wire sensors are accepted; the DP97 will automatically
recognise and select 3 or 4 wire mode. Display of input A, B OR a-B (differential) can
be selected; a differential “zero function” allows sensor accuracy differences to be
eliminated for accurate differential readings.
An RS232 interface (remote control and measure) is fitted as standard and isolation is
incorporated. An analogue (retransmission) output is also fitted as standard; the 1V dc
output is programmable between lower and upper set limits.
Calibrated sensors can have their calibration points programmed into the DP97 via a
personal computer using Labfacility software. The instrument then digitally self
calibrates to the probe(s) providing corrected temperature readout to give optimum
system accuracy.
The non-volatile memory ensures permanent retention of the values until the user
wishes to re-programme using the software, preventing unauthorised personnel from
changing the values.
Primary power is provided by an internal, re-chargeable sealed lead-acid battery, which
provides in excess of 12 hours operation from a full charge. A mains adapter is
provided for re-charging and for operation directly from the mains.
A range of precision stainless steel sheath Pt100 probes is available for the DP97.
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Front Panel Information at a Glance: when you switch on
To obtain a reading from a temperature sensor, select channel A or B (1) and select the
required units (2).
The appropriate indicator LED indicates the selected channel and units. For version 2.1,
the A and/or B LED indicators, according to the channel selected, cycle between a
steady on state and a brief off state (occulting) when corrections are stored and applied
to measurements (not applicable to version 1.4). To read differential temperatures from
two sensors, select channel A-B (1) and select the required units (2).
To set an A-B reading of zero to “null out” probe differences, press NULL (3).
Error Indications:
The DP97 has several modes of error indication according to internal or external
problems. Refer to section 3,4 for details.
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2. INSTALLATION
Back Panel
General
a) The standard version is for bench-top use. Retractable legs can be
extended to provide a convenient viewing angle.
b) The optional version permits the installation of the DP97 into a
suitable panel cut out.
Supply Connection
Primary power is provided by the internal, rechargeable sealed lead-acid battery which
provides up to 12 hours operation from a full charge. The external supply adapter for
recharging and also allows operation directly from a 220/240V 50/60Hz supply (or 110V
50/60Hz to special order). The output lead with its fitted connector is connected to the
appropriate rear panel mating connector.
Internal battery power can provide operation for up to 12 hours from full charge. Low
battery charge state is indicated by “bAtt” on the display.
Input Connections –Sensors
Platinum Resistance Thermometer(s) (Pt100) must be fitted with a high quality D-plug
and connected to INPUT A and/or INPUT B as required. A 3 OR 4 wire configuration
can be used but they are connected differently as shown. The DP97 will automatically
sense which configuration is employed.
Special care must be taken when connecting 3 wire resistance thermometer
terminations to the connector pins. A good crimp must be achieved to avoid Ohmic
contacts, which would result in reading errors. Only use good quality connectors with
gold contact material; the OMEGA D type is recommended.
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3. OPERATION
Ensure that the instrument is connected to a suitable supply or has charged batteries
and that the required input connections are made.
Switch “on” using the rear mounted rocker switch.
The display will show “Pr 2.1” or “Pr 1.4” the programme designation. There is a short
delay while internal checks are carried out, then the input A value will be displayed.
i) To read sensor temperature directly
a) PRT input A is automatically selected at switch-on. Brief repeated
key presses will step through the various functions or holding
the key depressed will auto repeat (scroll through); this applies
to the other functions as well.
Note: If for any selected channel, the sensor is either not connected or has a faulty
connection (including sensor open-circuit), the LED display will show:-“Err 3”
Press any button to resume normal operation (either select another channel or rectify
any fault and continue intended use).
b) Press CHANNEL to select inputs A,B or A-B (differential).
c) Press UNITS to display the desired units °C, °F, K, or Ω
ii) To read Differential Temperature
The difference in temperature between two PRT sensors can be obtained
by displaying A-B.
Ensure that the necessary sensors are connected to both A and B inputs
as required.
Press CHANNEL to select A-B
Press UNITS to display the desired units
The value now displayed is the difference between the input A and input B
(A-B) for the sensor type indicated.
Null Feature
For calorimetry and other applications to optimise the precision of differential
measurements, probe tolerances can be nulled by pressing the NULL key when in A-B
mode. This gives an A-B reading of zero when pressed regardless of any real difference
value.
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iii) Matching DP97 to Calibrated Sensors
It is possible to automatically match the DP97 to a Pt100 sensor with up to
10 dedicated calibration values. Such values, published in an associated
certificate indicate true Ωversus °C values corresponding to accurately
known reference temperatures. Up to 10 sets of values per sensor can be
fed into the instrument via the RS232 interface using the associated
software supplied with each version 2.1 instrument as standard.
By matching the instrument to a probe on this basis, “corrected”
temperature readings are obtained directly without the need for cross-
referencing to temperature/resistance tables or to the calibration
certificate. This is particularly helpful when taking differential (A-B)
readings.
Refer to sections 6 and 7 for details.
iv) Error Indications
The DP97 has several modes of error indication according to internal or
external problems as follows:
Display Cause
Err 1 Calibration lost (very unlikely)
Err 2 Software fault
Err 3 Broken probe connection
Err 4 RS 232 command error
BAtt “Low” battery
Or Over-range input
Ur Under-range input
Only Err 1 / Err 2 would require returning the instrument to our factory.
Note:During normal operation, if a selected probe is disconnected from the
instrument the display will indicate Err 3 (broken probe indication). If the same probe is
re-connected, Err 3 will remain on the display until any key is pressed.
v) ¾ Wire Recognition
DP97 requires a minimum of 80mΩlead resistance (eg. 1 metre of 7
stranded 0.2 mm² wire) to recognise a 4 wire probe. Otherwise the
instrument will default (perhaps incorrectly) to 3 wire mode.
If a simulator is used to apply resistance values to check or calibrate the
DP97 ensure that at least 80mΩof lead resistance exists between the
simulator and the D plug.
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If using a shorter leadout from the probe or thicker gauge cable, please
ensure that the DP97 is in the correct wire recognition mode. This can be
checked by pressing the SPAN ss button ONCE.
Two numbers will be displayed e.g. 3-4. The first digit being the X
parameter (e.g.3) and the second digit being the Y parameter (e.g.4).
These displayed numbers will only be displayed momentarily.
Caution, pressing the SPAN ss button more than once or holding it down
continuously will alter the X-Y setting.
X Parameter
This is a configurable parameter. If the probe configuration is 4 wire but
has a lead resistance of less than 80mΩper leg, he instrument may
recognise it as a 3 wire probe (showing 3-3); the SPAN ss may be used to
force the instrument into a 4 wire measurement mode by pressing SPAN
ss until X = 4. To verify, allow the DP97 to ead the currently selected
channel and press SPAN ss once; the display will now show 4-4.
X = 3 3 or 4 wire mode is allowable on either channel A or B i.e. A4, B3 or A3,
B4 or A3, B3 or A4; B4 (if both probes are 4 wire). I.e. 3 or 4 wire auto
Selected.
X = 4 4 wire mode is mandatory on both channels A & B I.E. A4, B4.
Y Parameter
The Y parameter gives the actual measuring mode of the currently
selected channel (except differential).
Y = 3 3 wire measuring
Y = 4 4 wire measuring
Differential Mode
In A-B mode the SPAN ss figure is not to be relied upon because the values
displayed will be for the last channel which has been read by the instrument and
this could be A OR B.
In order to verify status of each channel, select the channels A and B individually.
4. INSTRUMENT RE-CALIBRATION
Re-calibration of the DP97 is unlikely to be required routinely unless specified by user
regulations. If this is performed by someone other than the supplier, guarantee of
specification compliance may be invalid.

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The calibration kit option (two precision resistors) is required to perform re-calibration.
No additional instruments are required since the DP97 self-calibrates as follows:
Caution: Do not proceed unless specified resistors are available. Failure to do so
may invalidate the warranty.
a) With the supply disconnected, remove the instrument
case cover by removing the two screws on the rear
panel and sliding the cover off the rear of the
instrument.
b) Insert the jumper JP1 (shorting connector) –this
places the DP97 into self-calibrating mode.
Connect the supply and switch on*. Calibration is
simply a matter of connecting the precision resistors in
sequence. The necessary value of the resistor, together
with the input to which it has to be applied is indicated
on the display. The steps are as follows:
*At this point, the existing calibration has now been over-written by default
values. The procedure should therefore now be completed.
i) Connect 100 Ohm calibration resistor to PRT INPUT a.
ii) Press “SPAN ss ” and display will show a value close to 100 Ohms. If the
value shown is wrong by more than 1.00 Ohms, a fault exists and the
Instrument must be returned for rectification.
iii) Press “SPAN ss ” again and the instrument will compute the average value
of 16 readings of the resistor value.
iv) When the display reads “A = 250”, connect the 250 Ohm calibration
resistor to input A.
v) Press “SPAN ss ” and display will show a value close to 250 Ohms. If the
value shown is wrong by more than 1.00 Ohms, a fault exists and the
instrument must be returned for rectification.
vi) Press “SPAN ss ” again and the instrument will compute the average value
of 16 readings of the resistor value.
vii) Repeat steps (I) to (vi) for input B.
The DP97 then returns to a normal power-up state, PRT A, degrees C.

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Switch off the Instrument
1) Remove the jumper lead JP1. This is VITAL.
Should the instrument be switched on with JP1
In position, the calibration is lost.
2) Replace the instrument cover.
The instrument is now ready for normal use. The central processor is software
driven and no other adjustments or modifications should be attempted. If it is
necessary for the supplier to re-calibrate an instrument in consequences of
unauthorised persons so doing, a charge may be made accordingly
5. ANALOGUE (RE-TRRANSMISSION) OUTPUT
This output varies linearly between 0 and 1 volt dc. The output will be 0V whenever the
reading of the instrument is at or below the zero parameter as set by front panel button
pushes or RS232 commands. The output will be at 1 V whenever the reading is at the
span parameter as set by the user. Any reading between zero and span will result in an
Analogue output signal proportional to the position of the reading with respect o the
defined zero and span values. To set-up the output values:
1) Zero: Press “SHIFT” and “ZEROs” to raise the value (in current units) at which
a zero output will occur.
Press “SHIFT” and “ZERO tt ” to reduce the value in a similar way.
2) Span: Press “SHIFT” and “SPAN ss ” to raise the value (in current units)
at which a SPAN (1V) output will occur.
Press “SHIFT” and “SPAN tt ” to reduce the value in a similar way.
The size of the increment is 0.1 Ohm. This is necessary so as to eliminate the
requirements of working from degrees in temperature (K, C or F) back to Ohms. If
setting up in degrees, some odd looking numbers may occur on the display.
The output falls to 0V in the event of the selected span value being exceeded; this is
done to indicate such a condition.

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6. RS232 COMMUNICATIONS
General
Remote control will be seized by sending an RS232 character, and relinquished by
sending the LOCAL command. While in remote control the front panel buttons will be
locked out (inoperative) and the right hand decimal point will indicate remote operation
(local lock-out). RS232 parameters will be a fixed baud ate and word length. 9600
Baud, 8 Data, No parity, 1 stop bit.
Remote control of calibration has not been included. (Refer to section 4).
Protocol:
Command strings are limited to a single statementaction will occur on receipt of
The “end of line” character. All actions will return a status character followed by
Data if appropriate. The status will be “•” for a successful transaction; Other
values indicate syntax error, broken probe etc.
All commands may be abbreviated to their first two letters eg. UNITS OHMS
becomes UN OH. Input delimiters will be spaces or commas.

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Command set:
Display parameters: UNITS OHMS
UNITS C
UNITS K
UNITS F
INPUT A
INPUT B
INPUT A-B
Analogue parameters: SPAN Value in Ohms
ZERO Value in Ohms
Measurement: MEASURE
Return to Local: LOCAL
Output Protocol
Replies will depend on the command implemented, and will be numeric or –with
commas and spaces as delimiters. All replies will be terminated by CR and LF. The
first number will be an error code.
0No error
1Calibration lost (EEPROM corruption)
2
3Broken probe
4Syntax error
6
7
There will be no further numbers if:
a) There is an error
b) The primary command was UNITS, INPUT or LOCAL
Further output will be provided in the case of MEASURE, DUMP (DIAGNOSE).
1. MEASURE
Eg. If output is 0, 2351.7
First number -error code
Second number -value in units set by previous commands

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For digital probe matching within the instrument (version 2.1 only) additional
commands are used as follows:
CORRECTIONS A(turns OFF B corrections) Turns A on
B(turns OFF A corrections) Turns B on
AB (turns ON BOTH A & B corrections)
OFF (turns OFF BOTH A & B corrections)
Whatever is set by this command is retained during power-down.
LA Lists Ch A corrections
LB Lists Ch B corrections
CA Enter Ch A corrections
CB Enter Ch B corrections
Query Says “Not enabled”, “A”, “B”, “AB”
XX* Disables corrections
ENABLE* Enables corrections
IC Initialise corrections (i.e.Erase) –useful after installing software
*For these commands to be actioned theSPANss key must be pressed as the
command is typed.
Corrections entered as Follows
Type TM Sends
CA <CR> How Many Points
2 <CR> Entry=/0 Ohms
100,000 <CR> Deg C?
0.000 <CR> 0100.0000 Ohms 0000.0000 Deg C ok?
Y <CR> Entry=/1 Ohms
138.510 <GR> Deg C?
100.000 <CR> 0138.5100 Ohms 0100.0000 Deg C ok?
Y <CR> Done
This would repeat for more points.
Pressing N at the ok? Prompt will allow re-entry of the point.
Once entered, type LA OR LB TO SEE/CONFIRM CONTENTS.
Rules of entry.
1) Ohmic values must always increment from point to point
2) All values must be entered to THREE decimal places i.e:-.001,0.001,10.001 are all?
ok.
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Note: Use of the DP97 “CORRECTIONS PC SOFTWARE” supplied with the instrument
facilitate the correction procedure by means of a much simplified, user-friendly approach
described below.
7. USE OF CORRECTIONS PC SOFTWARE for Digital Probe Matching
a) Instrument set-up and software loading
PC Requirements: Any PC running in MS-DOS and having a 3½” disk drive,
mouse and mouse driver installed, (the software can be used without a mouse; use
up/down arrows and/or ALT key with the highlighted letter in each function box). A
printer will allow hard copies to be taken.
Using DP97 software & RS232 interface lead.
i) Connect the RS232 interface lead to the DP97 and to the PC according to the
Pin configuration shown in section 6).
ii) Switch on the instrument and PC
iii) At the C:\> prompt, select the drive (if this is the correct drive for the PC in
use) i.e. C:\a: “ENTER”
At the a:\> prompt type “TM-C” and “ENTER”. If using comms port 2, type
“TM-C/2”.
After the introduction screen, the MAIN MENU will appear (refer to MAIN
MENU diagram).
Note 1: These instructions are included in the software as the “text file” and can be
Viewed or printed out as required.
Note 2: Prior to despatch the DP97 and PC software should be “enabled” for normal
operation. In the unlikely event of a communications problem between the
two items, please perform the following procedure: With all set-up actions
completed the Main Menu on the PC screen, press theSPAN ss key on
the DP97 whilst simultaneously clicking on theenable button on the Main
Menu. To check, click the Query button and the status box should confirm
enabled. Normal operation can now be carried out.
Note 3: To prevent corrections being programmed into the DP97 click on disable
Button. See Note 2 to re-enable.
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b) Using the software
From MAIN MENU:-
To input calibration values into the DP97 (up to 10 may be used per channel):
º Click EDIT to obtain EDIT corrections menu.
º Enter values against #01 through #10 but note that
i) All 10 need not be entered
ii) When returning to main menu the Ù values are sorted into ascending order.
If the corresponding °C values are not in ascending order, the status box
will show Error.
iii) All values must be entered with up to three decimal places e.g. 0.001,
10.001 etc. Both °C and Ù values must be entered.
º Click return to Main Menu
º From Main Menu, click FILES to obtain Load/Save/Print Menu
º Click SPECIFY
º Key file name into ‘CURRENT SELECTION’ File names end with .COR eg.
EXPI.COR. If .COR is not keyed in, it will be added automatically when ENTER
is pressed or OK clicked.
Note: File name should be cross referred to probe serial number.
º Click SAVE to save file
º Click LOAD to load data
º Click RETURN TO MAIN MENU and note loaded values are shown under
“Calibration Points”
º Click CHANNEL A <-> B
º Click SEND to transmit correction values to DP97
º Click CORRECT A, B OR A + B to switch on corrections
Note: Red dot in lower right hand corner of DP97 display window lights during “comms”
activity.
º Observe Channel A/B status LED on DP97 occults to indicate corrections stored
Within defined range. If this does not occult, probe reading does not lie within
corrections range and corrections are not used.
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Stored values can be viewed at any time as follows:
º From Main Menu, click CHANNEL to select channels A OR B
º Click READ
Stored values can be changed at any time by repeating input procedure. Stored
Values can be cleared from the DP97 at any time as follows:
º From Main Menu, click CHANNEL A <-> B
º Click DISABLE
º Click PRINT in load/save/print menu to print out corrections. To exit programme
and return to DOS, click EXIT on Main Menu.
Note: Although the DP97 stores only one set of corrections for each channel, the
number saved in the software is limited only by available diskette space. Data for many
probes can thus be stored.
When using corrections the DP97 channel annunciation lights (A or B) will occult at 4
second intervals according to the channel selected. In A-B mode channel A and/or B
annunciation lights occult at 8 second intervals.
It is important to note that the DP97 will revert to its standard resistance versus
temperature values for Pt100 sensors and the channel annunciation light will illuminate
normally, ie.the instrument interpolates only and will not extrapolate to extend
corrections outside the range entered.
When calibrating probes alone, prior to programming corrections into the DP97, we
recommend calibrating at a point slightly higher and a point slightly lower (e.g. by 5°C)
than the maximum and minimum temperatures expected for the probe in use. This
ensures corrections are always applied during normal operation. We recommend a
minimum of three correction values are programmed. The DP97 corrects only in
temperature (°C, °F, K). The Ohms value is not affected. Therefore, when measuring in
Ohms in corrected mode channel annunciation lights will not occult.
SPECIFICATIONS
All values are valid for a nominal 110v/240v 50Hz supply and 20°C ambient temperature
(±2°C).
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General
Range/Sensor type Pt100 to IEC 751 (ITS 90 refers). –199.99 to 849.99°C.Ro=
100Ω. Two input channels, each 3 or 4 wire connection with
automatic recognition (with manual overrride).
Overall Instrument ±0.02°C ± 1 digit for range -200°C to +500°C.
Accuracy (4 wire) ±0.005% reading ± 1 digit for range 500°C to 850°C.
Overall System Better than ±0.04°C with TM-l250 precision probe accuracy
(4 wire) from -50°C to +250°C with 5 point NAMAS
calibration.
Linearisation
Conformity ±0.01°C.
Stability
(vs ambient
temperature) 0.0025°C/°C ambient change.
Warm-up Time Negligible under normal ambient conditions. Allow 5 to 10
minutes for full stability unless stored at low temperature,
then allow 30 minutes minimum.
Pt100 Sensor Current 0.5mA nominal.
Display Resolution 0.01°C, K, °F,Ω.
Measurement Units °C, °F, K,Ω(user selectable).
Measurement Modes Input A or B or A-B (differential). Null facility in A-B mode.
Custom Calibration
(via PC software) Up to 10 calibration values can be allocated to (via PC
software) channels A and B. Values are retained in non-
volatile memory until replaced by user.
Null Function Corrects differential temperature readout between the two
Sensors to zero.
Sensor Lead
Resistance 25Ωeach lead maximum.
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Supply
Internal rechargeable batteries. Mains 110/240V 50/60Hz,
adapter included. Battery charge life up to 12 hours with full
charge dependent on pattern of usage.

Charger requirement 10 –11.5V d.c. 1A.
Power Consumption 10W nominal. Max 20W when battery is charging.
Series Mode Rejection 60dB @ 50Hz (50mV rms applied).
Common Mode
Rejection 30V rms applied between input and earth produces no
measurable effect.
Ambient Temperature
Range 0-50°C non-condensing. Ensure stable temperature range
for best accuracy. Allow adequate warm-up time if moved
from region of low ambient temperature prior to use.
EMC Compliance Meets EMC regulations. RFI to BS EN50081-1, 1992 and
immunity to BS.EN 50082-1, 1992.
CE Compliance CE marked and compliant to current regulations.
Display 14mm LED, 5 DIGIT, 999.99 range.
Front Panel Controls 5 x membrane keys for user functions.
Input Connections 2 x Pt100.via “D” connectors
Mechanical
Mechanical/Case Metal bench-top. Optional panel mounting kit.
Dimensions 145 x 66 x 240mm deep.
Weight 1.5Kg approximately.
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