Digital frequency meter
-
Upload
amit-parcha -
Category
Devices & Hardware
-
view
667 -
download
1
description
Transcript of Digital frequency meter
![Page 1: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/1.jpg)
Digital Frequency Meter
By : Parcha Amit.K
Roll No: 2K13E21
Department of electronics
University of pune
![Page 2: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/2.jpg)
Contents• Introduction to Digital Frequency
Meter
• Basic Building Blocks of Frequency Meter
• Typical specifications of Frequency meter
• Applications
![Page 3: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/3.jpg)
Introduction To Frequency Meter
(UNIVERSAL COUNTER)
• Need Of Frequency Meter• A Digital Frequency Meter is a general-purpose, basic, digital
counter for measuring, setting, and monitoring frequencies, for counting random events, and for industrial counting applications.
• Among its many frequency measurement applications are the test, adjustment , and calibration of oscillators, telemetering equipment, i-f amplifiers and filters.
• With appropriate transducers, it can be used to measure such physical quantities as pressure, temperature, strain, and weight.
• In conjunction with an optical or magnetic pickup, it will measure rotational speed also.
![Page 4: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/4.jpg)
![Page 5: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/5.jpg)
![Page 6: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/6.jpg)
Basic principal of operation • A simplified block diagram, indicates the
principal circuits of the instrument and the signal flow paths.
• The input amplifier, pulse-forming circuits, and the five ring counting units perform the counting operation.
• The input amplifier increases the instrument sensitivity and input impedance.
![Page 7: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/7.jpg)
• The ring counting units are cascaded scale-of-ten circuits.
• Each unit is coupled to a Numeric indicator, which provides the digital display.
• The main gate acts as a switch either to pass pulses (open gate) or to stop the flow of pulses (closed gate).
• The gate is driven by the main-gate flip-flop.
![Page 8: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/8.jpg)
• Time-base pulses from the time-base divider switch the flip -flop between its two stable states to open and close the main gate.
• The crystal-oscillator output is shaped into a pulse-type waveform to drive the time-base divider circuits.
• The divider produces a train of pulses derived from the oscillator signal with a frequency of 10, 1 or 0.1 pulses per second as selected by the COUNTING TIME control.
![Page 9: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/9.jpg)
• The pulse train is fed through the time-base gate to the main gate flip flop.
• The time-base gate and time-base gate flip flop operate in a manner similar to the main -gate flip-flop and main gate.
• The time-base gate prevents a divider pulse from opening the main gate during the display-time interval.
![Page 10: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/10.jpg)
• A counting interval starts when the ring counting units have been reset, the time-base gate has opened, and a divider pulse arrives at the main-gate flip-flop to open the main gate.
• The counting interval ends when the next divider pulse is received.
• This pulse closes the main gate, starts the display interval by switching the time-base gate flip-flop to close the time-base gate, and activates the display-time generator.
![Page 11: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/11.jpg)
• In this condition the divider pulses are locked out and the indicators display the measurement.
• After a time interval determined by the DISPLAY TIME control, the reset-pulse generator is triggered, and the ring counters are reset.
![Page 12: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/12.jpg)
![Page 13: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/13.jpg)
Synchronies Gating For Counting
![Page 14: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/14.jpg)
Main Gate Requirements:
• As with any physical gate, the main gate of the counter does exhibit propagation delays and takes some finite time to both switch ON and OFF.
• This finite amount of switching time is reflected in the total amount of time the gate is open for counting.
• If this switching time is significant compared to the period of the highest frequency counted, errors in the count will result.
• However, if this switching time is significantly less compared to the period of the highest frequency counted, the error is not appreciable.
![Page 15: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/15.jpg)
Types of Measurement Error
• The ±1 Count Error(quantization error)• When an electronic counter makes a measurement, a ±1
count ambiguity can exist in the least significant digit. This is often referred to as quantization error. This ambiguity can occur because of the non-coherence between the internal clock frequency and the input signal.
![Page 16: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/16.jpg)
Quantization error
![Page 17: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/17.jpg)
• The Time Base Error
• Any error resulting from the difference between the actual time base oscillator frequency and its nominal frequency is directly translated into a measurement error.
• This difference is the cumulative effect of all the individual time base oscillator errors described previously and may be expressed as dimensionless factor such as so many parts per million.
![Page 18: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/18.jpg)
Trigger Error
• Trigger error is a random error caused by noise on the input signal and noise from the input channels of the counter.
• In period and time interval measurements, the input signal(s) control the opening and closing of the counter’s gate.
• This causes the main gate to be open for an incorrect period of time.
• This results in a random timing error for period and time interval measurements.
![Page 19: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/19.jpg)
Frequency Measurement Error
• The accuracy of an electronic counter is dependent on the mode of operation.
• The total frequency measurement error may be defined as the sum of its ±1 count error and its total time base error.
• The relative frequency measurement error due to ±1 count ambiguity is
• Df/f = 1/ fin
where fin is the input signal frequency.
![Page 20: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/20.jpg)
SPECIFICATIONS
• Hp - Model 5240A
(12.4 GHz Digital Frequency Meter)• FREQUENCY MEASUREMENTS:
• RANGE: 10 Hz to 12.5 MHz
• GATE TIME: 0.1. 1.0 s: 10 s on special order.
• SELF CHECK: Counts 1 MHz for gate time chosen.
• SIGNALINPUT :
• SENSITIVITY: 100 mV rms.
• MAX. INPUT: 2 V rms.
• IMPEDANCE: 1 MΩ shunted by 10 pF.
![Page 21: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/21.jpg)
• TIME BASE:FREQUENCY: 1 MHz
EXTERNAL INPUT: 1 V rms into 1kΩOUTPUT: 1 MHz , 2 V square wave into 6k
• REMOTE RESET: By grounding center of BNC back panel.
• ACCURACY : ± 1 count ± 1 timebaseaccuracy
• READSIN : MHz or GHz with positional decimal point .
• IMPEDANCE: 20kΩ each line.
![Page 22: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/22.jpg)
• BCD REFERENCE LEVELS:
GROUND: 5 V , 1kΩ source.
PRINT COMMAND: 0 V to 10 V step, dc coupled.
HOLD-OFF REQUIREMENTS:
+15 V max+ 2.5 V min.
PRICE:
Model 5240A. $4750
![Page 23: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/23.jpg)
Applications:
• Frequency Counting
• Precise frequency measurements in radar based application.
• Pressure, temperature, strain, and weight measurements with proper transducer.
• Motor speed measurements are also possible with proper arrangement.
• Microwave frequency measurements.
![Page 24: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/24.jpg)
Reference:
• “Basic Electronic Instrument Handbook”, Clyde Coombs, Editor, McGraw-Hill, 1972.
• Hewlett-Packard Journal, June 1974.
• GENERAL RADIO COMPANY
model TYPE 1150·A Manual
![Page 25: Digital frequency meter](https://reader038.fdocuments.in/reader038/viewer/2022102712/5595f88a1a28ab9e428b457e/html5/thumbnails/25.jpg)
THANK YOU