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Related Manuals for Omega 868F
Summary of Contents for Omega 868F
- Page 2 CE mark to every appropriate device upon certification. The information contained in this document is believed to be correct but OMEGA Engineering, Inc. accepts no liability for any errors it contains, and reserves the right to alter specifications without notice.
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Page 3: Table Of Contents
TABLE OF CONTENTS MODELS 868 AND 869 DIGITAL THERMOMETERS SECTION PAGE SECTION 1 INTRODUCTION ............1 General Description........................1 Features ..............................1 SECTION 2 INSTALLATION............1 Unpacking ............................1 Battery Installation........................2 SECTION 3 OPERATION ............2 Safety Precaution and Notes....................2 Control and Display ........................2 Operating Procedure ........................3 Accuracy Considerations ....................4 Three Wire and Four Wire Operations..............4 SECTION 4 THEORY OF OPERATION ........6... -
Page 4: Section 1 Introduction
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Page 5: Battery Installation
BATTERY INSTALLATION A nine volt battery is supplied with the instrument but is not installed, to avoid possible damage due to leakage during storage or shipment. Install the battery as follows: 1. Remove the instrument back cover. 2. Insert the battery in place; make sure correct polarity is observed and battery terminals are contacting the battery clips. -
Page 6: Operating Procedure
Figure 3-1. Control Layout, Model RATING PROCEDURE NOTE he instrument is factory set for wire operation. It can be asily changed for three wire use. Refer to paragraph 3.5. Connect the temperature probe to the input connector at the top of the instrument. Place the temperature range switch in the desired position. -
Page 7: Accuracy Considerations
jumper figure 3-2. - Page 8 NOTE gure 3-3 shows wiring schematics for three wire and four ire probe connections. Figure 3-2. Component Locations e 3-3. Three Wire and Four Wire Prove Connections...
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Page 9: Section 4 Theory Of Operation
SECTION 4 THEORY OF OPERATION This section contains a brief description of operation that should help a technician in understanding instrument operation during a measurement, to aid in isolating possible malfunctions. Detailed schematics of each model are provided at the end of the manual. THREE WIRE SIGNAL CONDITIONING Two phases are necessary to condition the signal for digitization. -
Page 10: Signal Phase
3. The input of A is connected to ground. The output of A equal to [A Vos]. 4. C is connected between the output of A and common. The voltage charged on C is equal to the output voltage of A or [A Vos]. -
Page 12: Four Wire Signal Conditioning
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. These are called the zero and signal phase. 4.2.1 Zero Phase During the zero phase, FETs are switched to configure the circuit... -
Page 13: Signal Phase
4.2.2 Signal Phase During the signal phase the 4 charged values of voltage are transfered to other parts of the circuit (refer to simplified Figure 4-4). The following explanations assume more than one charge transfer has taken place. 1. C is connected across C and after a sufficient number of zero and signal phases the voltage on C... -
Page 15: Low-Battery Detector
LOW-BATTERY DETECTOR Low-battery detection is accomplished by comparing the regulated voltage between V+ and common to the output of the voltage divider (R107 and R110), which is connected across the battery. When the battery voltage decreases, the output of the voltage divider rises above analog common, causing comparator U103A to change state. - Page 16 CAUTION Do not touch the elastomer contact strips or mating surfaces on the PC board. Also, use care when spreading the clips to avoid breaking them. 5. The instrument may be reassembled by reversing the above prodcedure, using Figure 5-1 as a guide. When assembling the instrument, take special note of the following points: A.
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Page 18: Calibration
Figure 5-2. Connections for Performance Verification and Calibration Table 5-1 Calibration MODEL 868 CALIBRATION ADJUSTMENT (°F) RESISTOR DESIRED STEP POTENTIOMETER RANGE VALUE (Ω) READING R104 200°F 93.03 Ω 00.0 R105 200°F 134.91 Ω 195.0 R103 1100°F 311.45 Ω 1100.0 MODEL 869 CALIBRATION ADJUSTMENT (°C) -
Page 19: Probe Compensation
PROBE COMPENSATION The procedure outlined in the last paragraph provides accurate absolute instrument calibration, but it cannot compensate for probe inaccuracy. Probe errors near 32°F (0°C) can be minimized by using the following procedure. 1. Make up an ice water bath by firmly packing a dewar flask or Thermos with pea-size ice cubes made of distilled water and then filling the container with distilled water. -
Page 20: Voltage Checks
5.4.1 Voltage Checks Several voltage checks can be made simply by connecting a DMM to various A/D converter IC pins. Table 5-2 summarizes these voltage readings. TABLE 5-2 VOLTAGE CHECKS REQUIRED STEP ITEM/COMPONENT CONDITION COMMENTS Connect DMM HI to +V Leave connected for all voltage checks. -
Page 21: Waveform Checks
5.4.3 Waveform Checks Several A/D converter waveform checks can be made using an oscilloscope along with the information in Table 5-3. 1. Connect 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. -
Page 22: Static Sensitive Parts
STATIC-SENSITIVE PARTS MOS devices are designed to operate at very high impedance levels. As a result, any normal static charge that builds up on your person or clothing may be sufficient to destroy these devices if they are not handled properly. Table 5-4 lists those parts used in the Models 868 and 869 that might be destroyed by static charge. - Page 23 jumper jumper...
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Page 24: Section 6 Specifications
FOUR WIRE SIGNAL CONDITIONING TABLE 5-5 PERFORMANCE VERIFICATION There are two phases necessary to condition the signal for (continued) digitization. Each phase lasts for a period equal to one-half of the MODEL 869 back plane period of the A/D converter. These are called the zero RESISTANCE ALLOWABLE READING and signal phase. - Page 25 SPECIFICATIONS continued MODEL 869 Three wire or four wire 100 Ω TEMPERATURE SENSOR TYPE: platinum RTD (alpha = .00385) 4 WIRE ACCURACY* SETTING RANGE RESOLUTION (18 °C TO 28 °C: 1 Year) ± 200 °C -100.0 °C to 199.9 °C 0.3 °C ±...
- Page 26 SPECIFICATIONS continued MAXIMUM COMMON MODE 42 V peak to earth. VOLTAGE: COMMON MODE REJECTION Less than 0.001°F/volt at dc, 50 and 60 Hz (Model 868): (100 Ω unbalance, LO driven). COMMON MODE REJECTION Less than 0.001°C/volt at dc, 50 and 60 Hz (Model 869): (100 Ω...
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Page 27: Parts List For Models 868 And 869
PARTS LIST FOR MODELS 868 AND 869 SCHEMATIC DESCRIPTION SCHEMATIC DESIG. LOCATION BA101 Battery, 9 V, NEDA 1604 C101 Capacitor, 0.1 F, 50 V, Ceramic Film C102 Capacitor, 0.1 F, 50 V, Ceramic Film C103 Capacitor, 0.1 F, 50 V, Ceramic Film C104 Capacitor, 0.1 F, 50 V, Ceramic Film C105... - Page 28 Jumper strip...
- Page 33 NOTES...
- Page 34 NOTES...
- Page 35 Customer Service Department will issue an Authorized Return (AR) number immediately upon phone or written request. Upon examination by OMEGA, if the unit is found to be defective it will be repaired or replaced at no charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser, including but not limited to mishandling, improper interfacing, operation outside of design limits, improper repair, or unauthorized modification.
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