Omega 868F, User Manual

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Page 2: ...ree in France 0800 4 06342 e mail france omega com Germany Austria Daimlerstrasse 26 D 75392 Deckenpfronn Germany Tel 49 07056 3017 FAX 49 07056 8540 Toll Free in Germany 0130 11 21 66 e mail germany omega com United Kingdom 25 Swannington Road P O Box 7 Omega Drive ISO 9002 Certified Broughton Astley Leicestershire Irlam Manchester LE9 6TU England M44 5EX England Tel 44 1455 285520 Tel 44 161 777...

Page 3: ...OPERATION 6 4 1 Three Wire Signal Conditioning 6 4 1 1 Zero Phase 6 4 1 2 Signal Phase 7 4 2 Four Wire Signal Conditioning 9 4 2 1 Zero Phase 9 4 2 2 Signal Phase 10 4 3 Analog to Digital A D Converter 11 4 4 Polarity Detector 11 4 5 FET Drivers 11 4 6 Low Battery Detector 12 SECTION 5 SERVICE INFORMATION 12 5 1 Disassembly 12 5 2 Calibration 14 5 3 Probe Compensation 16 5 4 Troubleshooting 16 5 4...

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Page 5: ...NOTE Use only 100 ohm platinum RTD sensors that conform to the DIN 43760 standard alpha 00385 Other type sensors will give inaccurate results Maximum allowable lead resistance for rated accuracy is 50 ohms per lead four wire or 10 ohms per lead three wire NOTE For best accuracy it is recommended that the instruments be used in the four wire configuration with a suitable four wire probe If three wi...

Page 6: ... when possible for best resolution and accuracy Power is automatically turned on when the range is selected Place the probe tip on or in the material to be measured The display will indicate the temperature at the tip of the probe in F model 868 or C model 869 An overrange condition a 1 followed by blanked digits may indicate the need to switch to a higher range or show that the temperature is out...

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Page 8: ...5 Figure 3 2 Component Locations e 3 3 Three Wire and Four Wire Prove Connections NOTE gure 3 3 shows wiring schematics for three wire and four ire probe connections ...

Page 9: ...converterback plane BP period Thesetwophasesarecalledthezerophaseandthe signal phase respectively During each phase appropriate FETs are switchedontoconfigurethecircuitasrequired 4 1 1 Zero Phase During the zero phase certain FETs are switched on to configure the circuit shown in Figure 4 1 This curcuit operates similarly to a sample and hold curcuit in which voltage levels are capacitively stored...

Page 10: ... a sufficient number of zero and signal phases the voltage on CE approaches that stored on CR That voltage is equal to IRR 2 CZ is connected between L2 and the input of A1 in a way that opposes the voltage drop across RT and L4 Since the voltage charged on CZ is I RZ L1 the voltage at the output of A1 is A1 I RT L4 I RZ L2 Vos or A1 I RT RZ L4 L1 Vos RZ is made to equal the value of RT at 0 This a...

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Page 12: ...geattheinputtoamplifierA1 1 CR is connected across RR The voltage charged on CR is equal to IRR 2 CZ is connected across RZ The voltage charge in CZ is equal to IRZ 3 The input of A1 is connected through L3 Since ideally zero current flows into A1 the voltage at the output of A1 is equal to A1 IL4 Vos 4 CC is connected between the output of A1 and common The voltage charged on CC is equal to the o...

Page 13: ...ce the voltage charged on CZ is IRZ the voltage at the output of A1 is A1 I RT L4 IRZ Vos or A1 I RT RZ L4 IRZ Vos RZ is made to equal the value of RT at 0 C This action eliminates the offset of RT 100Ω at 0 C 3 CD is connected between the output of A1 and the top of CD in such a way that opposes the output of A1 The voltage charge on CD is A1 I RT RZ L4 Vos A1 IL4 Vos or A1I RT RZ 4 CA is connect...

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Page 15: ... point you obtain access to replace the battery select three wire or four wire operation or perform calibration Replace cover 3 To remove the PC board unscrew the standoff securing the board to the front case The board may now be pulled free although the wires to the probe jack will still be attached When the board becomes free of the case the switch cover will pull free as well If necessary the b...

Page 16: ... A If the LCD was removed be sure it is aligned properly on the board with the clips fitted properly into the notch on each side of the board B If the probe jack was disconnected make certain the wires are connected properly The wire colors are marked on the PC board C Make sure the PC board is properly secured to the front case with the standoff The switch cover should be placed on the switch whe...

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Page 18: ...ENT F RESISTOR DESIRED STEP POTENTIOMETER RANGE VALUE Ω READING 1 R104 200 F 93 03 Ω 00 0 2 R105 200 F 134 91 Ω 195 0 3 R103 1100 F 311 45 Ω 1100 0 MODEL 869 CALIBRATION ADJUSTMENT C RESISTOR DESIRED STEP POTENTIOMETER RANGE VALUE Ω READING 1 R104 200 C 100 00 Ω 00 0 2 R105 200 C 174 00 Ω 195 0 3 R103 630 C 313 59 Ω 600 0 ...

Page 19: ...justed for a reading of 00 0 with the instrument on the 200 C range NOTE Using this method of probe calibration will uncalibrate the instrument slightly when used with other probes 5 4 TROUBLESHOOTING The troubleshooting information along with appropriate schematics and parts lists are included to serve as a guide to enable equipment repair The schematics and parts lists may vary slightly from act...

Page 20: ... IN HI of U102 and record the reading 4 Connect the DMM HI terminal to pin 30 IN LO of U102 and record the reading 5 Connect the DMM HI terminal to pin 35 REF HI of U102 and record the voltage 6 Connect the DMM HI terminal to pin 36 REF LO and record the reading Using the measured values above calculate the displayed reading neglecting the decimal point as follows Display 1000 IN HI IN LO REF HI R...

Page 21: ...ct the oscilloscope LO input to analog common U102 pin 32 2 Connect the oscilloscope HI input to the A D converter pin indicated in the table 3 Select an appropriate time base input attenuator setting and trigger mode to stabilize the display 4 Compare the displayed waveform with the corresponding drawing in Table 5 3 TABLE 5 3 WAVEFORM CHECKS ...

Page 22: ...ers only at a properly grounded work station Also ground yourself with a suitable wrist strap 3 Handle the devices only by the body do not touch the terminals or pins 4 Any PC board into which the device is to be installed must also be properly grounded 5 Use only anti static type solder suckers 6 Use only grounded soldering irons 7 Once the device is installed on the PC board it is normally adequ...

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Page 24: ...E READING RANGE C VALUE Ω 18 to 28 C 630 C 9 9 Ω 221 to 219 200 C 60 26 Ω 100 3 to 99 7 200 C 100 00 Ω 0 3 to 0 3 200 C 138 51 Ω 99 7 to 100 3 200 C 174 01 Ω 194 7 to 195 3 630 C 313 71 Ω 599 to 601 9 4 2 FOUR WIRE SIGNAL CONDITIONING There are two phases necessary to condition the signal for digitization Each phase lasts for a period equal to one half of the back plane period of the A D converter...

Page 25: ...oefficient 18 to 28 C time stability one year and errors with up to 50 Ω of lead resistance each lead Excludes probe errors however probe errors around 0 C may be compensated by an internal adjustment REPEATABILITY 0 1 C ambient temperature TEMPERATURE COEFFICIENT 18 to 28 C included in accuracy specification From 10 to 18 C and 28 to 50 C less than 0 015 C C MAXIMUM LEAD RESISTANCE each lead Four...

Page 26: ...L LIMITS FOR STORAGE Model 868 30 to 140 F less than 90 relative humidity up to 95 F linearly derate 1 5 RH F from 95 to 140 F ENVIRONMENTAL LIMITS FOR STORAGE Model 869 35 to 60 C less than 90 relative humidity up to 35 C linearly derate 3 RH C from 35 to 60 C RTD LINEARIZATION Ratiometric dual slope A D with continuous linearization INPUT CONNECTION Four pin miniature instrumentation connector P...

Page 27: ...47pF 500 V Silver Mica or Ceramic E2 C114 Capacitor 0 22 F 63 V Metalized Polyester E1 C115 Capacitor 0 22 F 63 V Metalized Polyester B2 CR101 Diode Silicon 1N4148 B1 DS101 Display LCD H4 J1001 Connector 4 tereminal Connector A3 mates with J1001 J1002 Connector Battery G1 J1003 Connector Battery G1 J1004 Connector Pin A3 J1005 Connector Pin A3 J1006 Connector Pin A4 J1007 Connector Pin A4 P1004 Te...

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Page 35: ... otherwise shall not exceed the purchase price of the component upon which liability is based In no event shall OMEGA be liable for consequential incidental or special damages CONDITIONS Equipment sold by OMEGA is not intended to be used nor shall it be used 1 as a Basic Component under 10 CFR 21 NRC used in or with any nuclear installation or activity or 2 in medical applications or used on human...

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