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.

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 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.

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 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.

Page 5

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.

Page 6

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.

Page 7

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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