Omega 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 instrum ent 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 b y 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.

Page 1

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.

Page 2

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.

Page 3

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 swit ch.
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 conn ected 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.

Page 4

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 Ω versus °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 cross­referencing 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 Recognitio n

DP97 requires a minimum of 80mΩ lead 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 80mΩ of lead resistance exists between the

simulator and the D plug.

Page 5

If using a shorter leadout from the probe or thicker gauge cable, please

ensure that the DP97 is in the correct wire recog nition 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 80mΩ per 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.