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Racal Instruments 2251A Operator's Manual

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Racal Instruments 2251A Operator's Manual

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  • Page 1 Artisan Technology Group is your source for quality new and certified-used/pre-owned equipment SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT • FAST SHIPPING AND DELIVERY Experienced engineers and technicians on staff Sell your excess, underutilized, and idle used equipment at our full-service, in-house repair center We also offer credit for buy-backs and trade-ins •...
  • Page 2 PUBLICATION DATE: SEPTEMBER 1998 Copyright 1998 by Racal Instruments, Inc. Printed in the United States of America. All rights reserved. This book or parts thereof may not be reproduced in any form without written permission of the publisher. Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...
  • Page 3 Authorization is required from Racal Instruments before you send us your product for service or calibration. Call your nearest Racal Instruments support facility. A list is located on the last page of this manual. If you are unsure where to call, contact Racal Instruments, Inc. Customer Support Department in Irvine, California, USA at...
  • Page 4 FOR YOUR SAFETY Before undertaking any troubleshooting, maintenance or exploratory procedure, read carefully the WARNINGS and CAUTION notices. This equipment contains voltage hazardous to human life and safety, and is capable of inflicting personal injury. If this instrument is to be powered from the AC line (mains) through an autotransformer, ensure the common connector is connected to the neutral (earth pole) of the power supply.
  • Page 5 This page was left intentionally blank. Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...

  • Page 6: Table Of Contents

    VXIbus Logical Address and Interrupt Level Assignment . 2251A Home State ....... .
  • Page 7 Reassembly Instructions ......4-17 2251A Input Amplifier Setup Procedure ....4-18 SECTION 5 APPLICATION NOTES .
  • Page 8 TABLES 2251A Home State ....... . 2251A Measurement Mode Output Strings ... . .
  • Page 9 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...

  • Page 10: General Information

    1.3 GHz with Option 41. 1.1.3 The 2251A is designed to be controlled remotely over the VXIbus. No local control of the counter is possible. The command set the counter responds to is defined by Racal Instruments. Refer to Section 3 of this manual for details of this command set.

  • Page 11: Measurement Functions

    Phase A rel B. This measures the phase difference between signals at inputs A and 1.2.1.11 Check mode. This mode allows the user to verify the 2251A is operating correctly. Note the capabilities of the Check mode may be extended by the use of special functions.

  • Page 12: Input Signal Conditioning

    Selection of the reference frequency is under software control. 1.3.2.3 Math Function. When the math function is active, the 2251A returns values of the form [ (Result - X) Y / Z ] where Result is a measured value, and X,Y and Z are constants entered by the operator.

  • Page 13: Options

    The following options are available for use with the 2251A. 1.4.1.1 Option 02M: Control Interface Intermediate Language (CIIL) interpreter. This option allows the 2251A to respond to the CIIL command set for use in MATE compatible test systems. Refer to Model 2251A-02M manual, Publication No. 980667.

  • Page 14: Performance Specifications

    Performance Specifications This section lists the performance specifications of the 2251A. 1.5.1 Input Characteristics Inputs A and B available as front panel BNC connectors. Input signal may also be routed to Channel A from any one of the internal analog SUMBUS lines on the VXIbus backplane.
  • Page 15 Input C (Option 41) Frequency Range: 40 MHz to 1.3 GHz Sensitivity (Sinewave): 25 mV rms to 1 GHz 50 mV rms to 1.3 GHz Dynamic Range: 40 dB to 1 GHz Input Impedance: 50 ohms (nominal) VSWR: < 2:1 at 1GHz Maximum Operating Input: 1 V rms Maximum Input Without Damage:...
  • Page 16 1.5.3 Measurement Functions 1.5.3.1 Frequency A & B Range: Input A: 6 x 10 Hz to 200 MHz Input B: 3 x 10 Hz to 160 MHz LSD: (1 ns / Gate Time) x Freq Resolution: ±(2 x LSD)±1.4 x (Trigger Error*/Gate Time) x Freq Accuracy: ±...
  • Page 17 1.5.3.4 Time Interval Separate Inputs: Input A start / Input B stop Input B start / Input A stop Common Inputs: Input A start / Input A stop Range: -2 ns to 1 x 10 sec Trigger Slopes: Start, positive or negative Stop, positive or negative LSD: 1 ns (100 ps with average mode)
  • Page 18 1.5.3.6 Frequency Ratio A / B Range, Inputs A and B: DC to 100 MHz LSD: (10 X Ratio) / (F x Gate Time) Resolution: ± LSD ± Trigger Error* B / Gate Time Accuracy: ± LSD ± Trigger Error* B / Gate Time 1.5.3.7 Frequency Ratio C / B (Only available with Option 41 fitted) Input C: 40 MHz to 1.3 GHz...
  • Page 19 Accuracy: ±Resolution ± Trigger Level Timing Error* ± Trigger Level Setting Error* at 10% Trigger point ± Trigger Level Setting Error* at 90% Trigger Point ± 2 ns ± (Timebase Error x Rise/Fall Time) 1.5.3.9 Pulse Width Range: 5 ns to 20 ms Positive Pulse Width: Start: + slope, 50% trigger point Stop : - slope, 50% trigger point...
  • Page 20 1.5.3.11 Time Interval Delay Programmable 200 Fs to 800 ms Time Interval: 25.6 Fs Resolution: ± 50 Fs ± 0.1% of reading Accuracy: 1.5.3.12 Peak Signal Measurement Indicates maximum, minimum amplitude or DC value of the measurement signal. Frequency Range: DC, 50 Hz to 20 MHz (useable to 100 MHz) Dynamic Range: 50 mV to 51 V pp...
  • Page 21 1.5.6 Gate Time 200 FS to 99.9 S Range: 25.6 FS Resolution: 1.5.7 External Standard Input (Not Available with Option 11) Frequency: 10 MHz Level: Min., 100 mV rms; Max., 10 V rms Max. Input Level: 400V peak to 500 Hz, decreasing to 10V rms at 30 kHz and above Impedance: 1 Kilohm (nominal) for signals <1V p-p,...
  • Page 22 1.5.9 Gate Out A TTL compatible signal coincident with the measurement gate is accessible to any one of the TTLTRGbus lines. The signal is low while the gate is open. 1.5.10 Temperature Performance Operating Temperature: 0 C to +50 C Storage Temperature: -40 C to +70 C 1.5.11...

  • Page 23: Definitions And Notes

    coupled. 1.5.14.2 Option 11 0.1 ppm Internal Reference Frequency 10 MHz Accuracy ± 1 x10 Warm-Up Time To within 1x10 in <3 minutes Temperature Stability 0.05 ppm, -10EC to 55EC Short Term Stability 3 x 10 /second # 0.1 ppm/year Aging Internal Reference Output nominal into 50S...
  • Page 24 1.6.5.1 The fractional deviation of the timebase frequency from 10 MHz is due to ageing, temperature, voltage variations, etc. This is determined by the reference frequency used by the 2251A. The default reference frequency is the VXIbus CLK10 signal. 1.6.6 Resolution &...
  • Page 25 Resolution (Number of Selected Digits) in Frequency, Period, Ratio, and Check (See Note 1) Gate Time 9 + Overflow 10 S 100 ms 10 ms 1 ms See Note 2 1 ms " " 1 ms " " 1 ms When setting the resolution by programming the number of digits, use the following formula to determine the value of the LSD (Least Significant Digit): LSD = F x 10 where F = Frequency and D = Number of digits rounded up to the...

  • Page 26: Safety

    Product Support Racal Instruments has a complete Service and Parts Department. If you need technical assistance or should it be necessary to return your product for servicing, call 1-800-722-3262 or call 714-859-8999 and ask for Customer Support. You may also contact Customer Support via E-Mail at: customer_service@rdii.com...
  • Page 27 1-18 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...

  • Page 28: Installation

    Address or the Interrupt Level. 2.4.2 To set the interrupt level of the 2251A, set switch S1 to the binary equivalent of the interrupt level selected. Interrupt levels between 0 and 7 inclusive are permitted. The OFF switch positions on S1 correspond to binary 1. The 2251A is shipped from the factory with the interrupt level set to 02.

  • Page 29: Installation

    2.5.2 To install the 2251A in a C size, VXI mainframe, ensure the 2251A has rear connector P1 oriented to mate with the corresponding connector on the mainframe backplane. Align the 2251A with the guides for the slot selected, and slide the counter into the mainframe.

  • Page 30: Using The Instrument

    USING THE INSTRUMENT VXIbus Control 3.1.1 Introduction This subsection provides programming information for the 2251A using the VXIbus interface. The VXIbus interface permits control of all the counter's functions. VXIbus Logical Address and Interrupt Level Assignment 3.2.1 Refer to Section 2.4 of this manual for instructions on setting the Logical Address and Interrupt Level.

  • Page 31: 2251A Home State

    2251A Home State 3.3.1 The 2251A Home State is the default configuration the 2251A will adopt on powering-up. Refer to Table 3.1 for details of the 2251A home state. Table 3.1 - 2251A Home State 2251A FEATURE DEFAULT SETTING Logical Address...

  • Page 32: Functional Check

    2251A using the Word Serial Write protocol of the VXIbus Specification (to which the counter conforms). The command WSRd indicates that data is to be read from the 2251A using the VXIbus specified Word Serial Read protocol.

  • Page 33: Output Message Format

    96. Refer to Sections 3.14 - 3.16 for more information about the Status Byte and Error Reporting. Output Message Format 3.5.1 The output strings generated by the 2251A are 21 bytes long. They are of the form: <aa> <±><nnnnnnnnnnnn><E><± >< m><cr>< f> where: <aa>...

  • Page 34: 2251A Measurement Mode Output Strings

    Positive Pulse Width A Negative Pulse Width A Phase A Rel B NOTE Option 41 must be fitted for the 2251A to be able to generate FC or RC. Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...

  • Page 35: Input Commands

    Input Commands 3.6.1 Introduction The 2251A responds to device-dependent commands in a "deferred" mode. This means the 2251A continues to accept commands until a terminating character or message is received; then, the entire string will be executed. To insure that the commands have been processed a “*OPC?”...

  • Page 36: Permitted Terminators

    3.6.2 Device-Dependent Commands The Device-Dependent commands for the 2251A are listed below, and grouped by category in the following tables. Table 3-5 Instrument Preset Conditions Table 3-6 Instrument Preset Code Table 3-7 Numerical Input Format Table 3-8 Measurement Function Codes...

  • Page 37: Instrument Preset Condition

    The Instrument Preset (IP) device dependent command aborts any measurement in progress, clears all buffers and registers, and returns all functions to the default condition. Table 3.5 provides the instrument preset condition for the 2251A following the device- dependent command (IP).

  • Page 38: Instrument Preset Code

    Table 3.5 - Instrument Preset Conditions 2251A DEFAULT FUNCTION COMMANDS Channels A and B Default Continuous Auto Trigger (If Auto- Trig Enabled) Recall Trigger Level (Not peak amplitude) Totalize A by B (If in TA function) Measurers Internal 10MHz Reference (If in CK) Two Character Header Enabled Table 3.6 - Instrument Preset Code...

  • Page 39: Numerical Input Format

    Table 3.7 - Numerical Input Format Byte No. Interpretation Permitted ASCII Characters Sign of mantissa + or - Most significant digit 0 to 9 or . Least significant digit Exponent indicator E or e Exponent sign/space + or - or space More significant digit 0 to 9 Less significant digit...

  • Page 40: Selecting The Measurement Function

    Negative Pulse Width A Phase A Rel B Check NOTE Option 41 must be installed in the 2251A for FC and RC to be accepted as valid commands. 3-11 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...

  • Page 41: Numerical Input Data

    Numerical Input Data 3.8.1 Table 3.9 provides the various numerical input ranges for each function and feature for the 2251A. Table 3.9- Numerical Input Ranges Numerical Limits Function Command High Code Set Resolution (Number of Digits) Trigger Level (Xl) SLA, SLB -5.1...

  • Page 42: Resolution Control Selection

    Resolution Control Selection 3.9.1 The 2251A provides a selection of resolution for frequency and time interval. In frequency, the resolution or number of digits displayed is related to the gate time. Refer to Section 1, Specifications for a description of the relationship between resolution, LSD, and accuracy.

  • Page 43: Signal Conditional Parameters

    3.10 Signal Conditioning Parameters 3.10.1 The following table lists the command codes for setting up the signal conditioning parameters on Inputs A and B. Table 3.11 - Input Control Codes Function Code FILTER Disable/Enable (Input A) AFD/AFE COM A Disable/Enable BCS/BCC DC/AC Coupling A ADC/AAC...

  • Page 44: Measurement Control Codes

    3.11 Measurement Control Codes 3.11.1 The 2251A offers a number of features which assist in setting up measurement features. Table 3.12 - Measurement Control Codes Function Code Enables Continuous measurement mode T0 (See NOTE 1) Enables Single (One-Shot)measurement mode T1 (See NOTE 2)

  • Page 45: Store And Recall Codes

    3.12 Store and Recall Codes 3.12.1 The 2251A permits the user to store and recall information about the setup and its parameters. Table 3.13 - Store and Recall Codes Function Code Recall unit type Recall master software issue Recall GPIB software issue...

  • Page 46: Special Functions

    3.13 Special Functions 3.13.1 The 2251A allows for extended capabilities by the use of special functions. Special functions are organized by decades, one for each of the nine mantissa output string digits. One special function from each decade may be entered into the special function register, but only the second digit of the special function number is stored.
  • Page 47 Table 3.14 - Special Function Codes SF Number Function Arming Start Stop Internal Internal External+ve Internal External-ve Internal External+ve External+ve External+ve External-ve External-ve External+ve External-ve External+ve Normal Operation Inputs A and B interchanged. Permits PERIOD B and TI B to A measurements, for example.
  • Page 48 Table 3.14 - Special Function Codes (Continued) SF Number Function Arming Start Stop Input A relay check (Must enable CK mode) Input B relay check (Must enable CK mode) Two Character header enabled Two character header disabled Table 3.15 - Using The Special Function Function Code Special functions Disabled/Enabled...

  • Page 49: 2251A Supported Ieee-488.2 Commands

    Preset the 2251A to a know state. See Table 3.5 - Instrument Preset Conditions 3.14.3 *TST? Command the 2251A to do an Internal Self Test. The response will be a 0 if the test passed and a 1 if the test failed. 3.14.4 *CLS Clears the Event Registers summarized in the Status Byte and all queues except the output.
  • Page 50 Return the 2251 (old status) Status byte. See Table 3.18 for the bit description. 3.14.16 When commanded by a GPIB slot 0; The 2251A responds to the GPIB SDC (Selected Device Clear) and DCL (Device Clear) commands by clearing its input and output buffers.

  • Page 51: Ieee-488.2 Status Reporting Model

    3.15 2251A IEEE-488.2 Status Reporting Structure Requirements The IEEE-488.2 Specification requires the implementation of the Status Data Structures. These are shown in Figure 3-1 which is a replica of Figure 11-8 in the IEEE-488.2 1987 Specification. Figure 3-1 IEEE-488.2 Status Reporting Model...

  • Page 52: Device Dependent Status Bit (Ddsb)

    DDSB (bit 0 of the Status Byte). 3.16.2 2251A SRQ Assertion The conditions for the 2251A to assert the DDSB (which would have been the SRQ bit of the old 2251 status byte) are as follows: Measurement cycle completed...
  • Page 53 3.16.3 2251A Status Byte The 2251A status byte is obtained in response to the *STA? command. The byte is eight bits wide, and the individual bits are interpreted as shown in Table 3.18. Table 3.18 - 2251A STA Response Description...

  • Page 54: Error Messages

    Error Messages 3.17.1 This section lists the errors the 2251A can generate. Refer to Table 3.19 for these messages, and an explanation of the cause of each error. Errors 50 to 58 may only be generated if the appropriate special function is enabled and the Check function is selected.

  • Page 55: Alphabetical List Of 2251A Command Codes

    Table 3.20 - Alphabetical List of 2251A Command Codes CODE RESPONSE Note: Underlines indicate power-up default conditions. Selects front panel Input A Selects SUMBUS Input A signal source Connects timebase reference to Input A Selects Input A AC coupling Disables Input A X10 Attenuator...
  • Page 56 Table 3.20 - Alphabetical List of 2251A Command Codes (continued) CODE RESPONSE Selects Input B DC coupling Sets Input B input impedance to 1 Megohm Sets Input B input impedance to 50 ohms Selects Input B manual trigger mode Sets Input B trigger to negative slope...
  • Page 57 Selects Fall Time A measurement mode *IDN? Identification Query, response is a ID string. Instrument Preset. Sets the 2251A to its power-up (Default) state. Refer to Table 3-1 for further details of the power-up state. Disables Math function (Default) Enables Math function...
  • Page 58 Recalls Input B trigger level Recalls memory setting n. Sets the 2251A to a previously stored configuration. n=0 to 9. Note all stored settings are lost on powering down the 2251A. 2251A configurations are stored by the SMn command code.
  • Page 59 Table 3.20 - Alphabetical List of 2251A Command Codes (continued) CODE RESPONSE Selects Rise Time A measurement mode Recalls unit type Selects Arming mode. Start: Internal Stop: Internal (Default) Selects Arming mode. Start: External +ve Stop: Internal Selects Arming mode.
  • Page 60 Increments of 20 mV and 200 mV are permitted in the X1 and X10 input attenuation modes. Stores the present configuration of the 2251A in RAM memory location n. n=0 to 9. Stored settings are recalled by the RMn command code. Note all stored settings are lost on powering down the 2251A.
  • Page 61 *TRG Trigger the 2251A to start a reading. Use with T1 mode *TST? Command the 2251A to do a Internal Self Test, response 0 = pass, 1 = fail *WAI Cause the 2251A to complete all pending commands before continuing 3-32 Artisan Technology Group - Quality Instrumentation ...

  • Page 62: Performance Verification

    PERFORMANCE VERIFICATION Performance Verification Procedures (PVPs) 4.1.1 This section provides the procedures necessary to verify that the 2251A conforms to its published specifications. It is recommended that these procedures are carried out at a minimum interval of one year. 4.1.2 The following conditions must be kept throughout the Verification Procedure.
  • Page 63 It is recommended that the following Special Functions are enabled in turn in the check mode and the results noted before commencing the Performance Verification Procedures for the counter. Successful completion of this procedure demonstrates that the 2251A measurement circuitry is functioning correctly. Frequency Measurement Check. Expected result: CK+10.000000000e+06 START TEC Short Calibration.

  • Page 64: Input A Low Frequency Sensitivity Test Configuration

    4.1.6 Input A Sensitivity Test 4.1.6.0.1 Set the 2251A to its home state. Select 50 ohms input impedance for input A and external frequency standard. (Command String: IP ALI B1) If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input.

  • Page 65: Input A High Frequency Sensitivity Test Configuration

    Figure 4-2, Input A High Frequency Sensitivity Test Configuration 4.1.6.5 Set the 2251A measurement resolution to the values given in Table 4-2 and apply the frequencies given to the counters input A. Verify that the 2251A gives a stable reading within the tolerances given at less than the signal level given.

  • Page 66: Input B Low Frequency Sensitivity Test Configuration

    Figure 4-3, Input B Low Frequency Sensitivity Test Configuration 4.1.7.2 Apply the frequencies given in Table 4-3 to the counters input B. Verify that the 2251A gives a stable reading within the tolerances given at less than the signal level given. Frequency Signal level...

  • Page 67: Input B High Frequency Sensitivity Test Configuration

    Figure 4-4, Input B High Frequency Sensitivity Test Configuration 4.1.7.4.1 Set the 2251A measurement resolution to the values given in Table 4-4 and apply the frequencies given in Table 4-4 to the counters input B. Verify that the 2251A gives a stable reading within the tolerances given at less than the signal levels given.

  • Page 68: Input C Test Configuration

    4.1.8.1 This section applies only to 2251As fitted with Option 41 (Input C) 4.1.8.1.1 Set the 2251A to its home state. Select Frequency C as the measurement mode and external frequency standard. (Command String: IP FC B1) If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input.

  • Page 69: Time Interval A-B Test Configuration

    4.1.9 Time Interval A-B Test 4.1.9.0.1 Set the 2251A to its home state. Select Time Interval A-B as the measurement mode, 50 ohms for input A input impedance, Common mode for inputs A and B and external frequency standard. (Command String: IP TI ALI BCC B1) If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input.

  • Page 70: Totalize A By B Test Configuration

    4.1.10 Totalize A by B Test 4.1.10.1 Set the 2251A to its home state. Select Totalize A by B as the measurement mode, 50 ohms input A input impedance and external frequency standard. (Command String: IP TA ALI B1) If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input.
  • Page 71 Ratio A/B Test 4.1.11.1 Set the 2251A to its home state. Select Ratio A/B as the measurement mode, 50 ohms for input A input impedance, DC input coupling for input B, external frequency standard and set the measurement resolution to three digits.
  • Page 72 4.1.12 Ratio C/B Test 4.1.12.1 Set the 2251A to its home state. Select Ratio C/B as the measurement mode, DC input coupling for input B, external frequency standard and set the measurement resolution to six digits. (Command String: IP RC ALI SRS6) 4.1.12.2...

  • Page 73: Input A Trigger Level Test Configuration

    4.1.13 Trigger Level Accuracy Test 4.1.13.1 Set the 2251A to its home state. Set the counter to DC input coupling for input A and enable special functions. (Command String: IP ADC SFEAAU) 4.1.13.2 Connect the counter to the DC standard as shown in Figure 4-10 and set the DC Standard output voltage to 5.000 V.

  • Page 74: Input B Trigger Level Test Configuration

    Figure 4-11, Input B Trigger Level Test Configuration 4.1.13.7 Reverse the polarity of the DC input to the counter, trigger the measurement and recall the stored trigger level value. Verify that it is -5.000 V ± 80 mV. 4.1.13.8 Disconnect the test equipment. 4-13 Artisan Technology Group - Quality Instrumentation ...

  • Page 75: Functional Checks

    Note the signal generator output level. 4.2.1.4 Enable the counters input A filter (Command code AFE) and verify that the 2251A no longer counts. Increase the signal generator until the counter gives a stable reading.Note the signal generator output level and verify that this level is approximately...

  • Page 76: Input A X10 Attenuator Check Configuration

    Enable the counters input A attenuator (Command code AAE) and verify that the 2251A no longer counts. Increase the signal generator until the counter gives a stable reading. Note the signal generator output level and verify that this level is approximately ten times the level previously noted.

  • Page 77: Input B X10 Attenuator Check Configuration

    Enable the counters input B attenuator (Command code BAE) and verify that the 2251A no longer counts. Increase the signal generator until the counter gives a stable reading. Note the signal generator output level and verify that this level is approximately ten times the level previously noted.

  • Page 78: Disassembly Instructions

    Slide the cover along the channel that it sits in, towards the rear of the counter and remove the cover. 4.3.3 Remove the ten panhead screws that secure the 2251A bottom cover to the counter side extrusions, five on each side. 4.3.4 Remove the three countersunk screws that secure the cover to the counter.

  • Page 79: 2251A Input Amplifier Setup Procedure

    4.5.1.1 This section provides the setup procedures that are to be carried out after repair of the 2251A or the failure of a routine specification check. 4.5.1.2 All setup procedures are to be carried out with the counters covers removed, at an ambient temperature of 23 C ±...

  • Page 80: Input A Amplifier Setup Configuration

    If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input. Configure the external signal source to accept the 10MHz reference from the 2251A. (Command String: FA ALI SRS3) 4.5.2.3 Connect the counter to the signal generator as shown in Figure 4-16.

  • Page 81: Input B Amplifier Setup Configuration

    (Command Code FB BLI SRS3 If Option 11 is installed connect the 2251A internal reference output to the external signal source 10 MHz Input. Configure the external signal source to accept the 10MHz reference from the 2251A.

  • Page 82: Input C Setup Configuration

    Turn off the signal generator output. Reduce the signal generator output level to 9.0 mV rms. 4.5.4.7 Turn on the signal generator output and verify that the 2251A is not counting. If the counter continues to count, repeat steps 5.5.5.4 to 5.5.5.7. 4.5.4.8 Disconnect the test equipment.
  • Page 83 ο operation for 4 hours at an ambient temperature of 25 +/-2 C Prior to calibration of the 2251, 2251A (with Option 11) place the module in a chassis which allows access to the frequency adjustment screw (Racal 1264C Chassis) or place the module on an extender card.

  • Page 84: Application Notes

    APPLICATION NOTES Programming Defaults In Automatic Functions The Model 2251A features a number of automatic functions, Pulse Width (both negative and positive), Rise/Fall Time and Phase. The purpose of these functions is to reduce the amount of code the end user must send to the counter to set up what are really complex measurements.

  • Page 85: Positive/Negative Pulse

    When in the automatic functions of Pulse Width and Rise/Fall Time, the signal being measured on the 2251A is on a single channel and the Common mode (BCC) is automatically enabled. Channel A and B inputs are internally connected to allow the counter to minimize propagation delay and mismatch.
  • Page 86 The following commands are toggle functions for the default signal conditioning parameters. Sending any of these to the 2251A with most of the automatic commands (PW, NW, RT, FT) enabled will cause the following to occur. COMMAND Parameter Set The 2251A will enable AC coupling on Channel A (and on Channel B due to Common) The 2251A will enable the filter on Channel A.
  • Page 87 Time Interval Negative Slope, Channel A Positive Slope, Channel B Channel A, DC Coupled The following commands, when sent to the 2251A while it is in the Negative Width (NW) mode will cause: COMMAND Parameter Set The 2251A will change to Positive Width (PW) mode and return a header of PW.
  • Page 88 Negative Slope, Channel A Negative Slope, Channel B Channel A, DC coupled The following commands, when sent to the 2251A while Fall Time (FT) is enabled will cause: COMMAND Parameter Set The 2251A will change to Rise Time (RT) with a header of RT, Channels A and B will have a positive slope enabled.
  • Page 89 The 2251A will remain the Fall Time (FT) mode with a header of FT and Channels A and B will have a negative slope enabled. Phase Measurement Phase measurement on the 2251A is a sequence of functions and is accomplished by measuring the time interval between the two signals and calculating the phase as a function of the total Period.
  • Page 90 Because of the default conditions and disallowed set-up parameters on the automatic functions of the 2251A, care needs to be taken when designing drivers or soft panels to ensure that correct transitions are made when changing functions or signal conditioning parameters.

  • Page 91: Calculating Measurement Cycle Time

    Measurement cycle time is a concern in systems that contain a large number of instruments or in systems where proper timing is crucial. The 2251A and the 2251A-02M are capable of a variety of measurement functions. All measurement functions are dependent on the measurement signal itself.
  • Page 92 MEASUREMENT TIME There are four basic functions for which measurement time can be calculated: frequency/period, time interval, ratio and phase. The equations to determine the actual measurement time for the four functions are as follows: Frequency/Period: Frequency/period measurement times are equivalent to the actual gate time. The actual gate time always exceeds the programmed gate time by up to 2 periods of the input signal.
  • Page 93 PROCESSING TIME After a signal has been measure, the counter requires time to process the information. The overhead introduced by the internal processing of the counter is 50 mS Processing Time: 50 mS MEASUREMENT CYCLE TIME Frequency/Period Measurements Example: Signal Frequency: 1 KHz = = >...
  • Page 94 TIME INTERVAL MEASUREMENTS Time interval measurements are highly dependent on the measurement signal. The user will need to approximate the time interval, rise/fall time, or pulse width of the measurement signal in order to calculate an approximate measurement cycle time. NOTE: Rise/fall time and pulse width measurements require auto-trigger EXAMPLE:...

  • Page 95: Phase Measurements

    PHASE MEASUREMENTS A phase measurement consists of: Ratio Measurement: To ensure that the two input signals are of the same frequency (within 10%) Period Measurement: to determine the period of signals Time Interval Measurement: To determine the time difference between two signals. Thus, the phase measurement time consists of the summation of the above three measurement times.
  • Page 96 Measurement Cycle = Processing Time + Trigger time + Meas. Time Measurement Cycle = 50 mS + (500 mS + 500 mS) + 2.004250 mS Measurement Cycle = 1.052004250 S An examination of the measurement calculations indicate that trigger times are a significant component of the measurement cycle time.
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  • Page 98 SECTION 6 OPTIONAL HARNESS ASSEMBLIES The following harness assemblies are used to connect Racal Instruments Model 2251A to Freedom Series Test Receiver Interfaces. Each harness documentation consists of an assembly drawing, parts list, system wire list and wire list. 407298 Virginia Panel, Inc.
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  • Page 104 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...
  • Page 105 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...
  • Page 106 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...
  • Page 107 6-10 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com...
  • Page 108 Racal Instruments REPAIR AND CALIBRATION REQUEST FORM To allow us to better understand your repair requests, we suggest you use the following outline when calling and include a copy with your instrument to be sent to the Racal Repair Facility.
  • Page 109 Support Offices Racal Instruments, Inc. 4 Goodyear St., Irvine, CA 92718-2002 Tel: (800) RACAL-ATE, (949) 859- 8999, FAX: (949) 859-7309 Racal Instruments, Ltd. 480 Bath Road, Slough, Berkshire, SL1 6BE, United Kingdom Tel: +44 (0) 1628 604455; FAX: +44 (0) 1628 662017...
  • Page 110 Artisan Technology Group is your source for quality new and certified-used/pre-owned equipment SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT • FAST SHIPPING AND DELIVERY Experienced engineers and technicians on staff Sell your excess, underutilized, and idle used equipment at our full-service, in-house repair center We also offer credit for buy-backs and trade-ins •...

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