AN795 Converter Datasheet

AN795 Datasheet PDF, Equivalent


Part Number

AN795

Description

Voltage to Frequency / Frequency to Voltage Converter

Manufacture

Microchip

Total Page 15 Pages
Datasheet
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AN795
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AN795
Voltage-to-Frequency/Frequency-to-Voltage Converter
Author: Michael O. Paiva,
Microchip Technology, Inc.
RATIOMETRIC MEASUREMENT (ANALOG DIVISION)
One of the most difficult circuits to build is one which will divide one analog signal by another. Two voltage-to-frequency (V/F) converters
can do such division with ease. The numerator is counted directly as a signal, while the denominator forms the time base.
V1 TC9400
V/F
V2 TC9400
V/F
÷N
One
Shot
Output = N
V1
V2
Latch
Counter
One
Shot
Reset
Latch
FIGURE 1: Ratiometric measurement (analog division).
RPM/SPEED INDICATOR
Flow rates and revolutions per second are nothing more than frequency signals, since they measure the number of events per time
period. Optical and magnetic sensors will convert these flows and revolutions into a digital signal which, in turn, can be converted to a
proportional voltage by the use of a frequency-to-voltage (F/V) converter. A simple voltmeter will then give a visual indication of the
speed.
Analog Display
Speed
Sensor
TC9400
F/V
(Optical or Magnetic)
FIGURE 2: RPM/speed indicator.
RPM
DVM Display
RPM
© 2002 Microchip Technology, Inc.
DS00795A-page 1

AN795
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AN795
MOTOR SPEED CONTROL
The motor's speed is measured with the F/V converter, which converts RPM into a proportional voltage. This voltage is used in a
negative feedback system to maintain the motor at the controlled setting.
V+
Speed
Set
FIGURE 3: Motor speed control.
Op
+Amp
TC9400
F/V
Motor
Pulse Type
Tachometer
(Optical or
Magnetic)
PROPORTIONAL FLOW-RATE CONTROLLER
A TC9400 F/V converter can be used to regulate the amount of liquid or gas flowing through a pipeline. The flow-rate detector generates
a pulse train whose frequency is proportional to the rate of flow through it. The F/V converts this frequency to a proportional analog
voltage which is used to drive the valve controller. The valve controller regulates the valve so that the flow is steady, even though
pipeline pressure goes up and down. A voltmeter connected to the F/V converter output will indicate the actual instantaneous flow rate.
Flow
Set
Valve
Valve
Controller
Flow Rate
Flow Rate
Detector
Pulse Output
TC9400
F/V
FIGURE 4: Proportional flow-rate controller.
Meter
DS00795A-page 2
© 2002 Microchip Technology, Inc.


Features www.DataSheet4U.com AN795 Voltage-to-Fr equency/Frequency-to-Voltage Converter Author: Michael O. Paiva, Microchip Tec hnology, Inc. RATIOMETRIC MEASUREMENT (ANALOG DIVISION) One of the most diffi cult circuits to build is one which wil l divide one analog signal by another. Two voltage-to-frequency (V/F) converte rs can do such division with ease. The numerator is counted directly as a sign al, while the denominator forms the tim e base. Latch V1 V2 TC9400 V/F TC9400 V/F ÷N One Shot Counter One Shot Reset Latch V Output = N 1 V2 FIGURE 1: Ra tiometric measurement (analog division) . RPM/SPEED INDICATOR Flow rates and r evolutions per second are nothing more than frequency signals, since they meas ure the number of events per time perio d. Optical and magnetic sensors will co nvert these flows and revolutions into a digital signal which, in turn, can be converted to a proportional voltage by the use of a frequency-to-voltage (F/V ) converter. A simple voltmeter will then give a visual indicati.
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