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Fluke 7250A Counter
Manufacturer:
Model:
7250A
Date:
1978
Class:
Type:
SubType:
Universal Counter Timer
Information
1-2. The Model 7250A is a Universal Counter-Timer capable of measurements in seven modes of operation: frequency (Channel A, 5 Hz to 80 MHz), period and period averaging (Channel A, 5 Hz to 1 MHz), time interval (Channel A to Channel B, 5 Hz to 2 MHz), counts per minute (Channel A, 5 Hz to 80 MHz), ratio of Channel A (5 Hz to 80 MHz) divided by Channel B(5 Hz to 1 MHz), and totalize Channel A (5 Hz to 80 MHz). In addition, Self Check mode is-provided to demonstrate operability of most 7250A circuits. 1-3. This manual documents the 7250A Universal Counter-Timer under two categories. The standard instrument without options and Accessories is covered in Sections 1 through 5, 7 and 8. All optional or accessory items are documented in Section 6; refer to Table 1-1 and 1-2 for a listing of available options and Accessories. Schematic diagrams for the standard instrument and the options are centralized in Section 8. 1-4. DESCRIPTION 1-5. The Model 7250A is a seven-digit universal counter-timer capable of measurements in frequency, period, period average, time interval, totalize, ratio, and self check mode. In addition, counts per minute mode offers a direct readout of RPM when the instrument is attached to an appropriate transducer. The 7250A features six manually selected resolution settings, autoranging, leading zero suppression, full annunciation, autoreset, and a free-air crystal time base. 1-6. Each of the two 1 Mfl input channels is controlled by a ± slope control and a three position trigger level offset switch. Separate attenuation controls (continuously variable from X1 to X100) are provided for each input. A 100 kHz low pass filter can be applied to both channels. Channel A can be measured in common with, or separately from, Channel B. Input frequencies on Channel A can range from 5 Hz to 80 MHz. Channel B, when used in ratio and time interval measurements, has a maximum input of 2 MHz. 1-7. A number of options and Accessories are available with the instrument. Improved time base stability can be realized with the optional TCXO, or with one of the oven time bases.

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Service and User Manual
Manual type:
Service and User Manual
Pages:
150
Size:
6.09 Mbytes (6381669 Bytes)
Language:
english
Revision:
Manual-ID:
P/N 487496
Date:
01 December 1978
Quality:
Scanned document, reading partly badly, partly not readable.
Upload date:
30 April 2017
MD5:
6b3a2e4ba0ec9eab84646c1ee4d67683
Downloads:
296
Information
Instruction Manual 1 INTRODUCTION AND SPECIFICATIONS ... 1-1 I-l. INTRODUCTION ... 1-1 1-4. DESCRIPTION ... I-l lr8. SPECIFICATIONS ... 1-1 2 OPERATING INSTRUCTIONS ... 2-1 2-1. INTRODUCTION ... 2-1 2-3. SHIPPING INFORMATION ... 2-1 2-5. INSTALLATION ... 2-1 2-6. Input Power ... 2-1 2-B. Instrument Case Mating ... 2-1 2-11. Tilt-Down Baü ... 2-2 2-13. Rack Installation ... 2-2 2-15. OPERATING FEATURES ... 2-2 2-17. OPERATION NOTES ... 2-2 2-19. AC Line Connection ... 2-5 2-21. Maximum Inputs ... 2-5 2-23. Counter/Timer Terminology ... 2-5 2-64. Function Control ... 2-8 2-66. Resolution Control ... 2-8 2-70. Separate/Common Control ... 2-8 2-72. Attenuation Control ... 2-9 2-74. Slope Control ... 2-9 2-76. Filter Control ... 2-9 2-78. Offset Control ... 2-9 2-80. Display ... 2-9 2-83. Accuracy ... 2-10 2-85. Dealing with One Count Error ... 2-10 2-87. Reducing Time Base Error ... 2-II 2-89. Trigger Error Considerations ... 2-11 2-91. Reducing Errors due to Noise on the Input Signal ... 2-11 2-93. Summary ... 2-12 2-95. OPERATING DIRECTIONS ... 2-12 2-97. Initial Procedure ... 2-12 2-99. Frequency Measurements (FREQ A) ... 2-12 2-101. Counts Per Minute Measurements (CPM X100A) ... 2-12 2-103. Ratio Measurements (RATIO A/B) ... 2-13 2-107. Period Measurements (PER A) ... 2-13 2-110. Period Averging Measurements (PER AVG A) ... 2-14 2-112. Time Interval Measurements (TI A-B) ... 2-14 2-118. Totalizing Measurements (TOT A) ... 2-15 2-120. Self-Check (CHK) ... 2-15 3 THEORY OF OPERATION ... 3-1 3-1. INTRODUCTION ... 3-1 3-3. FUNCTIONAL DESCRIPTION ... 3-1 3-5. Frequency (FREQ A) Measurements ... 3-2 3-8. Period (PER A) Measurements ... 3-2 3-11. Period Averaging (PER AVG A) Measurement ... 3-3 3-14. Counts Per Minute (CPM X100A) Measurement ... 3-4 3-17. Ratio (RATIO A/B) ... 3-5- 3-19. Totalize (TOT A) ... 3-5 3-21. Time Interval (TI A-B) ... 3-6 3-23. Self-Check (CHK) ... 3-6 3-25. CIRCUIT ANALYSIS ... 3-6 3-27. Power supply ... 3-6 3-29. Time Base ... 3-7 3-31. Input Circuitry ... 3-7 3-34. Function Logic ... 3-7 3-37. Resolution Logic ... , ... 3-8 3-41. Control Logic ... 3-9 3-46. Main Gate Clocking Logic ... 3-10 3-48. Main Gate Enable Logic ... 3-10 3-51. Count Circuits ... 3-11 3-54. Display ... 3-12 3-56. Time Interval Logic ... 3-12 3-59. Reset Logic ... 3-13 3-61. Remote Logic ... 3-13 4 MAINTENANCE ... 4-1 4-1. INTRODUCTION ... 4-1 4-3. SERVICE INFORMATION ... 4-1 4-6. GENERAL MAINTENANCE ... 4-1 4-7. Disassembly ... 4-1 4-9. Reassembly ... 4-3 4-11. Input Power ... 4-3 4-13. Fuse Replacement ... 4-3 4-16. Cleaning ... 4-3 4-18. PERFORMANCE TEST ... 4-4 4-20. Equipment Preparation ... 4-4 4-22. Time Base Accuracy Test ... ; ... 4-4 4-24. Sensitivity Test, Channel A ... 4-5 4-26. Sensitivity Test, Channel B ... 4-5 4-28. Display Test ... 4-6 4-30. Frequency A Test ... 4-6 4-32. Counts Per Minute Test ... 4-7 4-34. Ratio Test ... 4-8 4-36. Period Test ... 4-8 4-38. Period Average Test ... 4-8 4-40. Time Interval Test ... 4-8 4-42. Totalize Test ... 4-8 4-44. Self-Check Test ... : ... 4-9 4-46. CALIBRATION ... 4-9 4-48. Time Base Calibration ... 4-9 4-50. Coarse Time Base Adjustment ... 4-9 4-52. Channel A Trigger Level Adjustment ... 4-10 4-54. Channel B Trigger Level Adjustment ... 4-10 4-56. SELECTED COMPONENT REPLACEMENT ... 4-10 4-58. TROUBLESHOOTING ... 4-10 4-63. Static Discharge Precautions ... 4-11 5 LIST OF REPLACEABLE PARTS ... 5-1 TABLE OF CONTENTS ... 5-1 5-1. INTRODUCTION ... - ... 5-2 5-4. HOW TO OBTAIN PARTS ... 5-4 6 OPTION AND ACCESSORY INFORMATION ... 6-1 TABLE OF CONTENTS ... 6-1 7 GENERAL INFORMATION ... 7-1 7A MANUAL CHANGE INFORMATION ... 7A-1 8 SCHEMATIC DIAGRAMS ... 8-1 TABLE OF CONTENTS ... 8-1

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