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Valhalla 4176 Operation Manual

Programmable micro-ohmmeter
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Model 4176
Programmable Micro-Ohmmeter
Operation Manual
Need Help? Call 800-548-9806.
VA L H A L L A
www.valhallascientific.com
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©2015 Valhalla Scientific, Inc. All Rights Reserved.

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Summary of Contents for Valhalla 4176

  • Page 1 Model 4176 Programmable Micro-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. Valhalla Scientific, Inc. will repair the instrument during the warranty period provided it is return to our repair and calibration facility freight prepaid. No other warranty is expressed or implied.
  • Page 3 OCUMENTATION ISTORY 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 increases 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 AFETY YMBOLS Instruction manual symbol affixed to product. Indicates that the user W A R N I N G , R I S K must refer to the user manual for specific WARNING or CAUTION E L E C T R I C A L S H O C K . information to avoid personal injury or damage to the product.
  • Page 5 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 6 REFACE This manual contains installation, operating and programming, and configuration information for the Valhalla Scientific, Inc. Model 4176 Programmable µ-Ohmmeter. The manual consists of the following chapters: HAPTER NSPECTION AND NSTALLATION This chapter contains information on initial inspection, bench use and rack mounting instructions. It also contains the initial adjustments necessary to start operations.

  • Page 7: Table Of Contents

    3.3.4 HLC Relay Terminal......................16 3.3.5 RS-232 Connector......................... 17 ........................18 PPLYING OWER 3.4.1 Power-On Default Settings ....................18 4176.................... 19 ONNECTING A OAD TO THE ........................21 ANGE ELECTION ..................... 21 VERLOAD AND CHAPTER 4 MEASUREMENTS MODES AND FUNCTIONS............22 .....................
  • Page 8 Surface Probes........................43 5.3.4 Other Lead Sets ........................44 CHAPTER 6 REMOTE INTERFACE ....................45 INTRODUCTION........................45 CONNECTING THE 4176 VIA GPIB INTERFACE ............... 45 6.2.1 The GPIB interface capabilities: ..................45 6.2.2 Notes for GPIB installation ....................46 6.2.3 Computer’s Connection ......................
  • Page 9 CHAPTER 9 SPECIAL PROCEDURES.................... 76 ........................76 OISY EADINGS ........................76 NDUCTIVE OADS CHAPTER 10 THEORY OF OPERATION..................77 10.1 ......................77 OCALIZING THE ROBLEM 10.2 ...................... 77 OMPONENT EPLACEMENT 10.3 ....................78 ENERAL IRCUIT ESCRIPTIONS 10.4 ........................79 ROUBLESHOOTING 10.5 ...............

  • Page 10: Inspection And Installation

    2, notify the carrier's agent and the nearest Valhalla Sales Office. Retain the shipping carton for the carrier's inspection. DO NOT return equipment to Valhalla Scientific, Inc. or any of its sales offices prior to obtaining authorization to do so.

  • Page 11: Bench Use

    The rack mount kit consists of two brackets plus 4 flat head screws. The brackets are easily installed on the front end of each side rail as show in drawing № 4176-xxx in chapter 11. The kit is listed in chapter 5 as Option-R The size of the ohmmeter and the location of its center of gravity dictate that it must be supported on both sides along its entire length through the use of trays or slides.

  • Page 12: Safety Precautions

    1.6 Safety Precautions The power plug must be a three-contact device and should be inserted only into a three- contact mating socket where the third contact provides a ground connection. If power is provided through an extension cable, the ground connection must be continuous. Any discontinuity in the ground lead may render the unit unsafe for use! The testing of inductive loads such as transformers requires that special precautions be taken to avoid damage to the instrument and/or injury to the operator! Please refer to chapter 7.

  • Page 13: Chapter 2 Specifications

    Chapter 2 PECIFICATIONS The specifications for the 4176 Programmable µ-Ohmmeter are listed in the following paragraphs. In all cases the specifications are valid for full Kelvin Four-Terminal measurements using connections having less than 20mΩ of lead resistance per wire. 2.1 Standard Measurement Mode Specifications Table 2 –...

  • Page 14: Temperature Compensator Mode Specifications

    0.01 0.01 % of Full Scale % of Full Scale Figure - 20mΩ Range Error Graph Figure - 200mΩ to 20kΩ Range Error Graph 2.2 Temperature Compensator Mode Specifications Table – Temperature Compensator Mode Specifications The accuracy Accuracy specifications listed are Range <25°C >25°C...

  • Page 15: General Specifications

    2.3 General Specifications Display Type: ........................5 digits VFD A-to-D Conversion Rate:................... 45 conversions/seconds Display Update:......5 user selections (100msec, 200msec, 300msec, 400msec, 500msec) Overload: 20mΩ Range......................99.95% of range 200mΩ thru 20kΩ ....................119.95% of range Overload Indication: ..................flashes “OVERLOAD” Terminal Configuration: ....................Four-wire Kelvin Test Current Polarity: ................Positive (flows High to Low) Test Current Compliance Voltage:..................

  • Page 16: Chapter 3 Getting Started

    Before explaining how to make measurements, it is useful to describe the sections of the front and rear panel of the 4176. 3.2 Front Panel The front panel of the 4176 can be broken down into eight parts. In Figure 5 you can see the regions indicated by their name. Figure - 4176 Front Panel Sections 3.2.1 Power Switch...

  • Page 17: Display

    Displays the selected range or the auto range function is on, this section of the display will Range Window alternate between the automatically selected range and the word “AUTO”. Displays the Valhalla Scientific Logo. If a function is activated, this section of the display will Function Window alternate between the Logo and the abbreviated function name.

  • Page 18: Function/Numerical Keys

    PDATE PDATE The HLC key is used to enable or disable the 4176’s internal “Multi-Range Dual Limit Comparator. Also used to set and/or view the limits used. The A .

  • Page 19: Tcm Receptacle And Leds

    Values displayed while the fault indicator is illuminated are not to be considered valid in any case. The Omni Compensator is an optional accessory to the 4176. See chapter 5 section 2.1 for more detail.

  • Page 20: Hlc Leds

    In many applications the contact resistance can exceed the value of the load by several orders of magnitude. The 4176 bypasses this potential error source by providing two terminals of constant current and an additional two terminals for high impedance voltage sensing.

  • Page 21: Rear Panel

    3.3 Rear Panel The rear panel of the 4176 may vary from unit to unit according to the optional features installed. This section of the manual refers to the standard model without any optional features or modifications. If the 4176 that you are using features terminals or connectors not describe in this section, please refer to chapter 9 of this manual for addendums that reference the particularities of your model.

  • Page 22: Fuse Holder

    3.3.2 Fuse Holder The rear panel fuse holder provides access to the main power fuse. Fuse values are listed below: − Fuse − Fuse Replace blown fuses with their exact equivalent only! 3.3.3 Power Connector The 3-prong power connector on the rear panel of the ohmmeter is for the application of AC power to the instrument.

  • Page 23: Rs-232 Connector

    3.3.5 RS-232 Connector The RS-232 serial interfacing is done through the 9 pin female D-Sub connector located on the rear panel of the instrument. Knowledge of the specific pin functions of the serial connector may be necessary for certain applications; table 7 lists the pin assignment for the RS-232 connector.

  • Page 24: Applying Power

    3.4 Applying Power Before applying power, please refer to chapter 1 section 3. Turn on the ohmmeter by placing the front panel power switch in the ON position. If the ohmmeter does not to turn on, verify that the instrument is connected to the power line. If line power is not the problem, remove the power cord and check the line power fuse and the line voltage selection switch settings.

  • Page 25: Connecting A Load To The 4176

    The first step in using the ohmmeter is to connect to a load. Valhalla Scientific, Inc. offers a number of different test leads that can be used with the Model 4176 and other Valhalla ohmmeter models (see chapter 5 for a list of available test leads).
  • Page 26 Figure - Surface type probes For hard to reach surfaces, Valhalla Scientific offers three different sets of spring loaded dual needle probes that differentiate in overall size and distance between the needles.

  • Page 27: Range Selection

    As a safety precaution, the 4176 is designed to switch into Safe Mode if the overload persists for more then 10 seconds. In safe mode the 4176 shuts down its current source, and displays the word “SAFEMODE”...

  • Page 28: Chapter 4 Measurements Modes And Functions

    4.1 Standard Measurement Mode The 4176 powers on in the standard measurement mode, in this mode, the instrument simply measure the value of the applied load using a 4-wire configuration. This...

  • Page 29: Tcm" - Temperature Compensated Measurement Mode

    4.2 “TCM” - Temperature Compensated Measurement Mode Valhalla Engineers are pioneers in the technology of accurate measuring devices using recognized formulas that compensate for measurement inaccuracies as a result of environmental changes. The TCM feature simulates a constant ambient temperature chamber for materials which are normally subject to varying ambient temperatures.

  • Page 30: Omni Compensator

    TCM key. The display will briefly read “TCM OFF”. 4.2.3 TCS – Temperature Compensator Setup As describe in section 1.2 of this chapter, the 4176 needs to reference a temperature coefficient and a temperature reference to calculate the compensated value. Stored in the instruments memory are six configurations that can be selected.
  • Page 31 Temperature Temperature Material Configuration Coefficient Reference CU20 20°C Copper 3931ppmΩ/°C CU25 25°C AL20 20°C Aluminum 4030ppmΩ/°C AL25 25°C AG20 20°C Gold 3000ppmΩ/°C AG25 25°C The following procedure illustrates how to select one if these configuration and how to setup a customized configuration. This procedure does not need to be repeated every time the TCM mode is selected.
  • Page 32 Using the numeric keys, input a value for the temperature coefficient followed by the key. To input a negative coefficient, press the ± key. For corrections use the NTER key. LEAR After pressing Enter, the instrument will display the coefficient that you have typed. Check the value and press enter to confirm.

  • Page 33: Tcc - Temperature Compensator Calibration

    4.2.4 TCC – Temperature Compensator Calibration This procedure is used to match a 4176 with its Omni Compensator. The Temperature Compensator Calibration must be done in a temperature controlled area. When the readings stabilize, the instrument will automatically skip to the next screen.

  • Page 34: Hlc" - Hi-Lo Comparator Mode

    4.3 “HLC” - Hi-Lo Comparator Mode Another useful feature of the 4176 is the Dual Limit Comparator (HLC). This feature helps eliminate operator interpretation of ohmmeter readings. Operator error and fatigue are significantly reduced while realizing an increase in testing efficiency.

  • Page 35: Setting The Limits

    4.3.2 Setting the Limits Each range has a different set of limits that can be programmed by the user. Table 11 lists the default values programmed for each range. Once the user sets new values, the default settings will be overwritten and the user settings will be stored in memory. Table 11 - Default Comparator Limits Range Lower Limit...

  • Page 36: Hlc On

    Now the limits are set and will be stored in memory. Each range has a different set of limits that can be programmed by the user. Table 12 lists the default values programmed for each range. Once the user sets new values, the default settings will be overwritten and the user settings will be stored in memory.

  • Page 37: Update Function

    4.4 Update Function The Update function is designed to allow the user to set the display update rate and the display intensity. The user can chose from a list of five possible display update rates and eight levels of display intensities. The display update rate indicates the time interval in-between very display update.

  • Page 38: Run/Hold Function

    The values are stored in memory and the instrument will automatically return to the previous mode. 4.5 Run/Hold Function The Run/Hold function of the 4176 can be configured in three different ways: HOLD – Pressing the R key will freeze the readings on the display. The function window of the screen will flash “HOLD”.

  • Page 39: Configuring The Run/Hold Function

    4.5.1 Configuring the Run/Hold Function The Run/Hold function can be set to HOLD, PKHI or PKLO. Follow these simple steps to configure the function. Press the F . key followed by the R key. Using the numerical keys from 1 thru 3, select the action that you wish the Run/Hold function to use and press E NTER The screen will display:...

  • Page 40: Print/Log Function

    4.6 Print/Log Function The Print/Log function allows the user to receive the measurements through the instrument’s RS-232 or USB interface. A thermal printer/labeler or the HyperTerminal of a PC can be used to capture the readings. The measurements can also be log to an Excel spreadsheet by using a Data Sources Open Database Connectivity (ODBC) to access data from ohmmeter The Print/Log function can be configured in three different ways:...

  • Page 41: Configuring The Print/Log Function

    4.6.1 Configuring the Print/Log Function The Print/Log function can be set to PRINT, LOG or LOG2. Follow these simple steps to configure the function. Press the F . key followed by the P key. RINT Using the numerical keys from 1 thru 3, select the action that you wish the Print/Log function to use and press E NTER The screen will display:...

  • Page 42: View Function

    4.7 View Function The View function allows the user to view how the instrument’s functions are configured. This function is easy to use and is very useful especially for HLC and TCM users. 4.7.1 Using the View function Pressing the V key initiates the View mode.
  • Page 43 – The screen will display the configuration of the Run/Hold key. – The screen will display the configuration of the Print/Log feature. RINT TCM – The screen will display the temperature coefficient and temperature reference value set for the TCM mode. –...
  • Page 44 4.8 SafeMode As a safety precaution, the 4176 is designed with an optional Safe Mode feature. With the Safe Mode option activated, if an overload persists for more then 10 seconds, the 4176 shuts down its current source, and displays “SAFEMODE” on its screen. The ohmmeter does not automatically recover from safe mode;...

  • Page 45: Chapter 5 Optional Features And Accessories

    TTL compatible levels with a drive capability of 1 LS load. Also refer to chapter 7. 5.1.2 GPIB The Valhalla 4176 comes standard with a RS-232 interface. Also available is an optional GPIB IEEE-488.2 compatible interface. The interface is talk/listen, and provides range and ohmmeter function control.

  • Page 46: Accessories

    5.2 Accessories 5.2.1 Omni Compensator To be able to use the TCM feature of the 4176, the user will need an Omni Compensator temperature sensor. This item allows the ohmmeter to compensate for temperature variations when testing any material. 5.2.2 Option R: Rack Mount Adapter The 4176 µ-ohmmeters may be mounted in a standard...

  • Page 47: Test Leads

    5.3 Test Leads This section details the different test lead sets and connectors available for use with the 4176 µ-ohmmeters. All cables and test leads are manufactured by Valhalla Scientific Inc. and are tested before shipping. 5.3.1 Alligator Clip Type Leads 5.3.1.1 Option K: Kelvin Lead Set...

  • Page 48: Needle Type Probes

    5.3.1.3 Option C: Banana-to-Clip Cable Option "C" is a 48" general purpose shielded lead set terminated on one end in dual banana plugs and on the other end in black alligator clips. 5.3.2 Needle Type Probes 5.3.2.1 Option MP-1: Kelvin Micro-Probes Option "MP-1"...

  • Page 49: Surface Probes

    5.3.2.3 Option MP-S: Single Pointed Probe Set Option “MP-S” is a 48-inch shielded cable set with a 1A test current capacity employing a set of single pointed handheld pencil type probes. (2 wires to each point) 5.3.3 Surface Probes 5.3.3.1 Option MP-4: Surface Probes These probes permit...

  • Page 50: Other Lead Sets

    5.3.4 Other Lead Sets 5.3.4.1 Option BBL: Banana-to-Banana Cable Option "BBL" is a 48" shielded cable terminated on both ends in dual stacking banana plugs. This cable may be used for voltage and current connections to the ohmmeter. 5.3.4.2 Option SL-48: Low Thermal Leads Option "SL-48"...

  • Page 51: Chapter 6 Remote Interface

    6.1 INTRODUCTION The 4176 is a fully interactive automatic measurement system. Communication between the 4176 and host computers is easily accomplished. The standard RS232 interface or optional GPIB and USB interface provide the capability to automate testing, retrieve actual resistance readings in different formats, retrieve temperature measurements, log data, and also calibrate the 4176.

  • Page 52: Notes For Gpib Installation

    Manufacturer, model number, serial number and firmware version in the following format: VALHALLA SCIENTIFIC 4176,1.01G,0" If you do not receive a proper response from the 4176, please check if the power is on, the GPIB address is correct, and all cable connections are active.

  • Page 53: Connecting The 4176 Via Rs232 Interface

    The RS232 interface provides a point-to-point connection between two items of equipment such as a computer and the 4176. There are some parameters you need to set on the both sides. Once you have set these parameters, you can control the 4176 through the RS232 interface.
  • Page 54 Table 14 – RS-232 Connector Pin Configuration Pin # Pin Function No connection Receive Data (RxD) (input) Transmit Data (TxD) (output) No connection Signal Ground (GND) No connection No connection No connection No connection Figure 17 - Wiring Configuration DB9 to DB9...

  • Page 55: Connecting To A Computer

    Manufacturer, model number, serial number and firmware version in the following format: VALHALLA SCIENTIFIC 4176,1.02C,0" If you do not receive a proper response from the 4176, please check if the power is on, and all cable connections are active.

  • Page 56: Input And Output Queue

    LF for PC to judge message terminator. 6.5.2 Entering Commands The standards that govern the command set for the 4176 allow for a certain amount of flexibility when you enter commands. The 4176 does not adhere to any friendly listening standards so the commands and queries must be typed as specified.

  • Page 57: Synopsis Of Commands

    6.5.5 Synopsis of Commands The tables in this section summarize the commands of the programmable 4176 Ohmmeter. 6.6 DETAILS OF COMMAND REFERENCE Each command in this chapter will give a detailed description. The examples of each command will be provided and what query form might return.
  • Page 58 :SYST:ERR? QUERY Sends the System Error value to the remote host. Cleared with *CLS<crlf> Syntax: :SYST:ERR? Example: :SYST:ERR?<crlf> Response: 1F<crlf> Power-on default = 0 ADDRS COMM Sets the GPIB address in RAM memory not in non-volatile memory. Syntax: ADDRS <decimal address> Response: <crlf>...
  • Page 59 BCD COMMAND Selects BCD mode on or off Syntax: BCD <ON or OFF> Example: BCD ON<crlf> BCD?<crlf> ON<crlf> Power-on default = OFF Note: BCD mode on puts the logic level BCD on the rear panel connector and the ranges on the relays outputs. See chapter 7 for BCD connector pin-outs and relay descriptions.
  • Page 60 CNFG COMMAND Turns on and off system configuration items. Alarms, key beeps, other features. Syntax: CNFG <item number>, <ON or OFF> Example: CNFG 1, ON<crlf> CNFG? 1<crlf> ON<crlf> 1 - Supress Alarms 2 - Supress Key Beeps Power-on defaults = OFF CNFG QUERY Responds with CNFG mode on or off Syntax:...
  • Page 61 FAULT QUERY Returns the alarm bit mapped byte. Syntax: FAULT? Response: 2 digit Hexadecimal number FAULT_ALARM_NO_FAULT FAULT_ALARM_OVER_TEMP Internal temperature too high FAULT_ALARM_CAL_LIMIT Input level for calibration exceeded limit FAULT_ALARM_TCM Input level for TCM calibration exceeded limits FAULT_ALARM_CMD_CHAR Unprintable characters received or cmd too long FAULT_TXBUF_SPACE Low on space in transmit buffer...
  • Page 62 HLCHI COMMAND Sends the Hi-Lo Comparator High Limit for current range. Syntax: HLCHI <value> Where value = 1.0000 for 1 Ohm in the 3 Ohm range and 100.00 for 100mOhm in the 100m Ohm range, and 00.500 for .5k Ohms in the 20kOhm range.
  • Page 63 Send RANGE command before sending this command. Power-on default = Depends on range. *IDN? QUERY Returns the IEEE or RS-232 identification string from non-volatile. Syntax: *IDN?<crlf> Response: ID string "VALHALLA SCIENTIFIC 4176,1.01G,0" Example: *IDN?<crlf> "VALHALLA SCIENTIFIC 4176,1.01G,0"<crlf> ID_STRING "VALHALLA SCIENTIFIC" VERSION "1.01G"...
  • Page 64 KEY COMMAND Presses a key from the interface, use for macros when the command you desire is not listed here. Syntax: KEY <key number> Response: <crlf> (only after the key has been processed) Key number = 0 - 24 KEY_NO_KEY KEY_RANGE_1 KEY_0 KEY_4...
  • Page 65 KEY? QUERY Returns the decimal number of the key last key processed by the state machine. This query returns any key in the remote mode even if the key is locked out by remote mode, i.e. KEY_LOCAL is not locked out. Syntax: KEY?<crlf>...
  • Page 66 LOCAL COMMAND Returns meter to local mode, remote LED off, Goto Local. Syntax: LOCAL Returns: <crlf> Power-on default = LOCAL mode Notes: REMOTE mode selected when meter receives valid character (not <crlf>. Once selected, all keys are disabled and will not be scanned.
  • Page 67 OHMS? QUERY Responds with reading from front panel display causes immediate update of the conversion so repeated query requests gets most accurate data. Send range command or AUTO prior to sending this to get the scaling factor. The Ohms omega, milli and kilo characters are removed during remote formatting.
  • Page 68 RANGE QUERY Returns the selected range. Syntax: RANGE? Response: Range number = 0 - 7 0 = RANGE_OFF (SAFE MODE) 1 = R20mOHM 2 = R200mOHM 3 = R2_OHM 4 = R20_OHM 5 = R200_OHM 6 = R2K_OHM 7 = R20K_OHM A = RANGE_AUTO Power-on default = 7 RDNG? QUERY...
  • Page 69 RESET COMMAND Executes a soft reset of the ADuC834 processor system. Syntax: RESET Response: Front panel display show soft reset initiation. "RESETTING" is displayed flashing inverse mode for 300ms while all system configurations are returned to power up default. Example: RESET<crlf>...
  • Page 70 *STB? QUERY Returns the command status byte. Syntax: *STB? Response: Command status number = 0 - 0xFF Example: *STB?<crlf> 01<crlf> Fragment: TCM ON<crlf> *STB?<crlf> TCM AFF<crlf> **STB?<crlf> (returns * ERROR) 03<crlf> TCM?<crlf> ON<crlf> 0 = CMD_LAST_COMPLETE 1 = CMD_UNKNOWN 2 = CMD_MISSING_PARAM 4 = CMD_INVALID_PARAM 8 = CMD_MODE_OFF 16 = CMD_INCORRECT_NUMBER_PARAMS...
  • Page 71 TCM COMMAND Selects TCM mode on or off Syntax: TCM <ON or OFF> Example: TCM ON<crlf> TCM?<crlf> ON<crlf> Power-on default = OFF TCM QUERY Responds with TCM mode on or off Syntax: TCM? Example: TCM?<crlf> ON<crlf> Response: <"ON" or "OFF"> Power-on default = OFF Send this...

  • Page 72: Chapter 7 Bcd Interface

    The signals are TTL compatible ( , and ) and will drive 1 LS TTL load. 7.2 BCD Pin Assignments DATA This is the BCD coded data which is identical to that being displayed by the 4176. Pin # FUNCTION 1000 2000...
  • Page 73 RANGE Pin # FUNCTION Table 15 - RCD Range Truth Table PIN 30 PIN 11 PIN 29 PIN 10 Range Ranges OFF 20mΩ 200mΩ 2Ω 20Ω 200Ω 2kΩ 20kΩ OVERLOAD – PIN 12 This is a logic 1 when the data on the lines above is an overload indication. (Note: The Data is arbitrary during this condition.) AVDD &...
  • Page 74 Pin # FUNCTION Pin # FUNCTION 1000 2000 4000 8000 10000 20000 OVERLOAD AVDD AVDD AVDD AVDD AVDD AGND AGND AGND AGND Table 16 – BCD Pin Assignment Reference Table...

  • Page 75: Chapter 8 Routine Maintenance

    8.1 General This Chapter provides general maintenance information and a procedure for calibrating the ohmmeter. The Model 4176 µ-ohmmeter should be calibrated on a routine basis (every 12 months is recommended) to ensure continued accuracy. Before performing the calibration procedure below, the ohmmeter should be allowed to warm up at a stable temperature for at least 30 minutes with the covers in place.

  • Page 76: 4176 Calibration Procedure

    The sense calibration and the final adjustment calibration is cover-on and automated; the instrument will prompt the user throughout the steps. The source calibration is performed by adjusting six potentiometers located on the 4176 main board. All three calibrations must be performed for a complete calibration of the 4176.
  • Page 77 When the instrument has completed the zero cal for all the ranges, the screen will prompt the following message: Step 4. Apply 10mV using the voltage standard and press E to start the NTER 20mΩ range voltage calibration. Press the C key if you wish to LEAR return to the zero cal.
  • Page 78 When the instrument has completed the 10mV cal, the screen will prompt the following message: Step 5. Apply 300mV using the voltage standard and press E to start the NTER range voltage calibration. Press the C button if you wish to return to LEAR the previous screen.
  • Page 79 Step 10. Adjust RV3 for a display reading equal to the value of the load. Step 11. Select the 20Ω range. Step 12. Connect the 4176 to a 10Ω standard resistor Step 13. Adjust RV4 for a display reading equal to the value of the load.
  • Page 80 8.4.1.3 Final Adjustments Step 1. Select the 20mΩ range. Step 2. Connect the 4176 to a 10mΩ standard resistor. Step 3. Press F key followed by the C key. Step 4. Press the C key again to enter the ohms cal mode.

  • Page 81: Periodic Maintenance

    8.4.2 Periodic Maintenance The 4176 ohmmeter does not require any periodic maintenance other than an occasional cleaning of the exterior surfaces of the product and routine performance of the calibration procedure. Loose dirt or dust which may have collected on the exterior surface of the ohmmeter may be removed with a soft cloth or brush.

  • Page 82: Chapter 9 Special Procedures

    Chapter 9 PECIAL ROCEDURES 9.1 Noisy Readings In general, noisy readings are caused by poor connections either to the input terminals or to the test load. If noisy readings are encountered, check these connections first. 9.2 Inductive Loads The measurement of highly inductive loads (such as large transformers) may also yield noisy readings.

  • Page 83: Chapter 10 Theory Of Operation

    • Use only the specified replacement component or its exact equivalent. Spare parts can be ordered from your nearest Valhalla Scientific Service Center or from the factory directly by referring to the Valhalla Stock Number listed in the Parts Lists section at the back of this manual.

  • Page 84: General Circuit Descriptions

    10.3 General Circuit Descriptions The ohmmeter may be divided into four separate parts. 4176 Main Board (4176-700) – This portion of the ohmmeter contains the power supply and the constant current source. Power Supply – This section converts the AC line power into the DC levels necessary to power the ohmmeter’s circuitry.

  • Page 85: Troubleshooting

    Display – This is the visual interface to the user. The display receives its data directly from the micro-controller. Keypad Board (4176-701) – This section of the ohmmeter contains the keypad and the LED indicators for the TCM and HLC function.

  • Page 86: Current Source Detailed Circuit Descriptions

    +5V AVDD (analog 5 volt supply) and AGND (analog ground) AVDD and DVDD are regulated by a precision 5 volt regulator and isolated from each other as shown below. The complete power supply circuitry is shown on schematic 4176-070 sheet 1.

  • Page 87: Constant-Current Source

    The design of the current source compensates for all series resistance (within compliance voltage limits) to overcome the effects of test lead and contact resistances. The complete current source circuitry is shown on drawing 4176-700 sheet 2.

  • Page 88: Micro-Controller Board Detailed Circuit Descriptions

    10.6 Micro-Controller Board Detailed Circuit Descriptions Complete circuitry is shown on schematic 834u-070 sheet 1 thru 7. 10.6.1 Micro-Controller The micro-controller executes the analog to digital conversion on the voltage across the load. Also all other processes, such as range selection, HLC relay switching, LEDs activation and so on.

  • Page 89: Tcm

    10.6.3 The zener diode D5 and its associated components create a +1.2V reference. This voltage level plus AVDD are used to power the temperature compensator if attached. Refer to schematic 834u-070 sheet 1. 10.6.4 Reset U4, SW1 and Q1 form the reset circuitry for the micro-controller and the display. To reset, press SW1.

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