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Summary of Contents for Valhalla Scientific 4021
- Page 1 Model 4021 Digital Ohmmeter Operation Manual Need Help? Call 800-548-9806. VA L H A L L A www.valhallascientific.com ©2015 Valhalla Scientific, Inc. All Rights Reserved.
- Page 2 The warranty period for this instrument is stated on your invoice and packing list. Please refer to these to determine appropriate warranty dates. We will repair the instrument during the warranty period provided it is returned to Valhalla Scientific, Inc. freight prepaid. No other warranty is expressed or implied.
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Page 3: Safety Symbols
Documentation History All Editions and Updates of this manual and their creation date are listed below. The first Edition of the manual is 1. The Edition Number increments by 1 whenever the manual is revised. Updates, which are issued between Editions, contain replacement pages to correct or add additional information to the current Edition of the manual. -
Page 4: Warnings
REMOVE POWER and do not use the product until safe operation can be verified by service-trained personnel. If necessary, return the product to Valhalla Scientific for service and repair to ensure that safety features are maintained. -
Page 5: Table Of Contents
Chapter 4 Optional Equipment Chassis & Final Assembly Available Options Option BCD Assembly Test Leads Interface Chapter 11 Schematics & Drawings 4021-070 1 of 4 Chapter 5 Operations General 4021-070 2 of 4 Front Panel 4021-070 3 of 4 Rear Panel... -
Page 6: Chapter 1 General Information
General Information Introduction This manual has information to perform Inspection, Installation, Measurement Operations, and Troubleshooting for Valhalla Scientific Model 4021. Also included in this manual are: Specifications, Parts Lists and all Schematics. Manual Description This manual is separated into the 11 following Chapters. -
Page 7: Instrument Description
1.9999 MΩ. Four-wire resistance measurement is explained in more detail in Chapter 5. The 4021 is available with a variety of test probes, accessories, and a BCD data output (see Chapter 8). The 4021 is also capable of being operated from an internal heavy-duty battery pack (optional). -
Page 8: Chapter 2 Unpacking And Installing
Valhalla Scientific or any of its sales offices prior to obtaining authorization to do so. Power Requirements The standard Model 4021 is fitted for operation from an AC power source such as municipal AC line power. It may also be modified for operation from an internal rechargeable battery pack. - Page 9 If the unit is to be installed in a rack, assemble the ohmmeter into the rack mount adapter (Option R4) using the instructions included with the option. Then it is only necessary to locate the unit in the rack and make the power source and test lead connections. The unit should be operated only in areas where the ambient temperature does not exceed 50°C.
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Page 10: Chapter 3 Specifications
Chapter 3 Specifications This section lists the operating and accuracy specifications for Valhalla Scientific Model 4021 Digital Ohmmeter. Accuracy is valid at 25°C ± 5°C for a period of one year from the date of calibration. Range/Resolution/Test Current/Accuracy Table 1... -
Page 11: Power Specifications
Power Specifications Power Source (Standard AC): 115 or 230 VAC, ±10%, 50Hz – 400Hz Power Source (Optional DC): 4 rechargeable Ni-Cad Batteries 1.2V 4000mA/H Battery Charger (Standard with DC) Provides 6VDC at 300mA nominal Physical Specifications Width: 9.5” / 24cm Depth: 11”... -
Page 12: Chapter 4 Optional Equipment
HDB. One Option "A" is provided if the 4021 has been fitted with Option "HDB". Additional adapters may be ordered as needed. Option R4: Rack Mount Adapter Option "R4" is an adapter tray that allows the Model 4021 to be installed in a standard 19" equipment rack. Test Leads Option K: 4-Wire Kelvin Lead Set Option "K"... -
Page 13: Interface
Valhalla Model 1248. (See Chapter 8) Model 1248: Dual-Limit Comparator The Valhalla Model 1248 may be used in conjunction with a 4021 and Option BCD above. The Model 1248 is a dual-limit BCD comparator that interprets the display indications of the ohmmeter as either "HI", "LO"... -
Page 14: Chapter 5 Operations
Front Panel Power Switch Power is applied to or removed from the internal circuits of the 4021 by this switch. On battery operated units, this switch does not need to be turned OFF in order to charge the batteries. Range Switch The Model 4021 input range is selected by depressing the desired button on a multi-station interlocking push-button array located on the right-hand side of the front panel. -
Page 15: 4-Wire Resistance Measurements
In many applications the contact resistance can exceed the value of the load by several orders of magnitude. The 4021 bypasses this potential error source by providing two terminals of constant current and an additional two terminals for high impedance voltage measurement. -
Page 16: Connections
If the display appears to be erroneous when connected to a load, recheck the test leads for integrity and cleanliness. If all external items appear to be functioning properly, the problem may be the ohmmeter. In this case, please contact your local Valhalla Scientific Sales Office. -
Page 17: General
4021. If the Model 4021 exhibits problems that cannot be eliminated by reviewing Chapter 3 and 5, the following guidelines have been established to help solve the problem. -
Page 18: Circuit Descriptions
As it is not possible to anticipate all failure modes of the 4021, servicing personnel should become familiar with this section to gain a complete understanding of the internal workings of the Model 4021. -
Page 19: Constant Current Source
The -5V supply is regulated by IC2 from the -10V supply mentioned above. The +5Vb supply is regulated by IC3 from a +10V resultant from the DC-to-DC converter composed of Q1, Q2, T1, D8, D9 and associated components. Constant Current Source The constant current source is composed of IC4, IC5, Q4 and the precision resistor R26 and R28 –... -
Page 20: Transconductance Amplifier
10mA, just as it was through the jumper when the output terminals were shorted. Analog to Digital Converter The Analog to Digital conversion in the Model 4021 is aloud by IC 7 and its associated components. The reference voltage applied to IC7-2 is 1Volts. 1.2Volts are generated buy D16 and adjusted by R40 before being applied to IC7-1. -
Page 21: Led Display
LED Display The signal converted by IC9 is applied to four 7 Segment LEDs (DS2-DS5) and a ±1 LED (DS1). Concurrently, driver transistors Q5 through Q9 are turned on in sequence. This sequence is repeated at the 120 kHz rate, and the data display consequently appears to be continuous. Figure 4 LED Display Pin Function... -
Page 22: Chapter 7 Routine Maintenance
General This section of the manual contains routine maintenance information regarding the Valhalla Scientific Model 4021 Digital Ohmmeter. Calibration should be performed on a regular basis to ensure continued instrument accuracy. The recommended calibration interval is 1 year. Required Test Equipment Following is a list of the standard resistors and other equipment required to calibrate the Model 4021. -
Page 23: Calibration Procedure
Calibration Procedure The 4021 should be allowed to warm-up for a minimum of 5 minutes before beginning the procedure. The adjustments are accessed by removing the four feet screws, then lifting off the top cover only. The locations of the adjustments are shown on drawing number 4021-700 in Chapter Voltmeter Adjustment 1. -
Page 24: Battery Replacement Instructions
Battery Replacement Instructions (For DC powered instruments only) The rechargeable NiCad batteries used in the 4021 are very durable and should provide years of trouble-free operation. As with all batteries, replacement will eventually be necessary. Batteries may be ordered from Valhalla Scientific as stock #05-10117, quantity: (4). -
Page 25: Chapter 8 Interface Operations
Chapter 8 Interface Operations BCD Interface Option BCD has a rear mounted 50 pin Amphenol connector providing data in a parallel binary- coded-decimal (BCD) format. The outputs are TTL compatible and may drive 1 LS load. The summary of pin functions is provided below and on the schematic number 2053-076 at the back of this manual.
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