capmeter1c

+- 1

2

34.5V

8

4

OUTPUT

4

21

3+-

8

+-

5

76

4.5V

+9V

+9V

20KHz

TRIANGLE SIGNAL GENERATOR

CURRENT TOVOLTSCONVERTER

POSITIVE PEAKDETECTOR

RIPPLE FILTER

5VPP

25uS

dV/dT = 5v/25uS = 200,000v/sec

POSITION CLOSETO Cx CAP

POLY CARB CAP

OR NPO CERAMIC

2V PP FOR 10pF

DRAWN BY: DAVE JOHNSON

LF412

A1A

A2A

A2B

LF412

LF412

4.5V

+9V

SELECT VALUE FOR2VPP AT 10pF Cx

INGND

OUT

78L09

12V +9V

+4

2

3

8- 1LMC6482

+

4

2

38

-1

X2.5AMP

LMC6482

A3A

+9V

+9V

7

-

5

6

+GROUNDREFERENCEDSIGNAL

0V = 0pF

X2+5V @ 10pF

LM6482

A3B

A4A

IN GND OUT

TOP VIEW

+9V

ADJUST FOR ZEROVOLTS AT FINALOUTPUT WITH MINIMUMCAPACITANCE

7.8V

5.5V AT 10pF

ADJUST FOR 5 VOLTSAT FINAL OUTPUTWITH MAXIMUMCAPACITANCE

+9V

-

8+LM311

4 A1A

3

27

+9V+9V

+9V

20KHz

+9V

DAVID JOHNSON AND ASSOCIATES

0pF - 10pF

LOW VALUE CAPACITANCE METER

CAPACITANCECHANGE

CAPMETER1C.DSN A

LOW VALUE CAPACITANCE METER

B

1 1Sunday, December 12, 2004

Title

Size Document Number Rev

Date: Sheet of

+TANT4.7uF

0.1uF

0.1uF

10K

10K

0.47uF

200K

+TANT4.7uF

10K

220K

0.1uF

7.5K

200K

0.01uF 1M

150K

220K

0.1uF

0.047uF

10.0K1%

0.1

U?C

4071B8

910

U?D

4071B12

1311

U?B

4071B5

64

U?A

4071B1

23

680

0.1uF10K

1K1%

10K1%

3.9pF

ZERO ADJ

2K

4.02K1%

CX

10.0K

1%

4148

SPAN ADJ

5K

0.1uF

0.0015uF

10K1%

10K

0.1uF

0.1uF

CxTO Cx

TO Cx Cx