"Capacitor Capacity Tester, Capacitance Meter
Keywords: capacitive capacity tester
This is a more complex circuit. But when you make it. You have a tester that can be used to measure the maximum capacitance capacitance in the radio. The capacitor is not like a resistor to mark the impedance value on the housing, and many capacitances are not marked on the housing. There are also some old capacitors that have been wiped out during use. This instrument can measure the capacity of these capacitors. For electrical technicians, old radio enthusiasts and radio enthusiasts are good helper.
A common 555 timer is the core component of this circuit. Its action is to charge the measured capacitor (CX) to a fixed voltage, and then the capacitor is discharged through the loop, and the current table measures current flowing over 47Ω resistors. Because the 555 timer repeats this process several times per second. Keep the pointer of the current table stabilizes.
The current will vary depending on the size of the capacitance capacity. That is, the current table pointer will be correspondingly deflected according to the capacity of the measured capacitor, that is, the ratio of the capacitance capacity and the line current is linear. Just like the multimeter used to measure voltage and current. '
This table has five gear, from 100pf to 1μF, switching through a two-pole five block switch, in addition, switch X10 is used to measure a large capacity capacitor, and the current is divided into two channels, measured by 100 pF, 1000pF, 0.01μF, 0.1μF. Or more than 1μF or higher capacitance display is more accurate.
The accuracy of the components is not very perfect. Even the best devices, general nine resistors also consider 2% error. If there is no OA47 diode, it can be replaced with OA91 or OA95 gerodic diode. This circuit is loaded into a plastic box. Almost the same as the multimeter. But it is a bit better. Under financial license, the tester's measuring instrument should be as big as possible because it determines the accuracy of the measurement display. The current meter range you purchased is 0 ~ 50 micro, but the scale is from 0 to 100 (ie the original scale 10, 20, 30, 40, 50, 20, 40, 60, 80, 100), you can Modify with white correction or small sheet of paper.
Install the components on a printed circuit board, 555 integrated blocks are connected to a socket for easy replacement when needed. The connection line should be as short as possible, otherwise the stray capacitive of the line reduces the accuracy of the measurement. '
You can use a known capacity capacitor to sample the tester, you can find a known capacity of the capacitance, and test a few times. If the display is incorrect. Very simple, just buy a few different capacitances, in which one close to the nominal capacity is used to correct it. The individual gear is accurately corrected with a few closer nominal capacitance.
When corrected, the X10 is disconnected (ie, both switches are disconnected), and a nominal capacitance is accessed. Hand the switch to the appropriate range. Adjust 47kΩ fine-tuning resistor until the capacity of the capacitor is accurately read. Then, the switch will change, and the reading will change, adjust the 10kΩ fine-tuning resistance, so that the readings of the readings, for example, if you measure a 0.01μF nominal capacitor, in 0.1μF, the reading is 10, The reading at this time should be 20.
if not. For a capacitor equal to the corresponding gear capacity (eg 1000 pF, 0.01 μF, 0.1 μF, etc.). Regulate the gear (ie 1000 pF, 0.01 μF, 0.1 μF, etc.) so that the number displayed is full. (100). T close the switch X1O, the reading of the pointer will decrease, adjust the fine-tuning resistor 470KΩ, so that the reading of the pointer is 10. Then, a gear (e.g., from 0.01μF to 1000pf), the readings of the pointer should be 100. If not 100, adjust the 470Ω fine-tuning resistor until 100 is 100. At this time, the calibration of the capacitor tester is completed, you can try to measure the capacity of other capacitors to verify the accuracy of the correction.
Careful measurement, the accuracy of most ranges can reach 5%.
The switch X10 is used to measure a capacitance of 10 μF and a large capacity; switch × 0.5 makes the reading more accurate when the capacitance of the smaller capacity is measured.
Capacitance Meter
This Project Is Complex, However, When Finished, You Will Have An Instrument Capable of Measuring All But The Largest Capacitors Used in Radio Circuits. Unlike Variable Resistors. Most Variable Capacitors Are Not Marked with Their Values. AS Well. The Markings of Capacitors from Salvaged Equipment OFTEN RUB OFF. By Being Able To Measure THESE UNMARKED Components, this Project Will Prove Useful to the constructor. Vintage Radio Enthusiast OR. Antenna Experimenter.
The Common 555 Timer IC Forms The Heart of The Circuit (Figure Three). ITS Function Is To Charge The Unknown Capacitor (CX) To a fixed voltage. The Capacitor Is The Discharged Into The Meter Circuit. The meter the current being drawn through the 47 ohm resistor. The 555 Repeats The Process Several Times A Second. So That The meter nesedle remains steady.
The deflection on the meter is Directly ProPoryal To The Value of The Unknown Capacitor. THIS Means That The scale is linear. 1IKE The Voltage and Current Ranges on an an analogue multi-meter.
The meter Has Five. Ranges, from l00pf to luf, selected by a, five position two pole switch. In Addui, There Is A X10 Switch for Measuring Higher Values and A Divide - by · -Two Facility To Allow A Better Indication On The Meter Where The Capacitor Being Measured IS Just Above 100, 1000PF, 0.01, 0.1 or 1UF.
Component Values Are Critical. For best Accuracy, It is desirable That the nine resistors wire a to the range switch. IF 0A47 Diodes Are Not Available. Try OA91 or OA95 Germanium Diodes INSTEAD. CONSTRUCT The Meter in a plastic box; one this is about the size of your multi-meter but desk deeper is ideal. THE METER MOVEMENT SHOULD AS LARGE AS YOUR BUDET Allows You Will Be Using It To Indicate Exact Values. The meter you buy will have 50 microamperes. This Scale Needs to He Converted To READ 0 TO 100 (IE 20, 40, 60, 80, 100 Instead of 10, 20, 30, 40, 50). Use of white correction fluid or small pieces of paper will help here.
The Components Can Be Mounted on a Piece of Printed Circuit Board. Use a socket for the icsidement replacement Ever be needed. Keep Wires Short to Minimize Stray Capacitance: Stray Capacitance Reduces Accuracy.
Calibrating The Completed Meter Can Be Done In Conjunction with a Ready-Built Capacitance Meter. Failing this, a Selection of Capacitors of Known Value, As Measured ON A Laboratory Meter Could BE. IF Neither Of Sestions Are Available, Simply Buy SEVERAL CAPACITORS OF THE SAME VALUE AND USE The One Which IS Nearest The average as your standard reason. Use several standards to verify acid on all Ranges. Be
To Calibrate, Disable Both The XL0 and Divide-by-Two Functions (IE Both Switches Open). THEN Connect One of Your Reference Capacitors and Switch To An Approate Range. Vary the setting of the 47k trimpot. Until the meter is reading the exact value of the amount-by-two function. This will change the ready. Adjust the 1ok trimpot so what the nesedle shows exactly twice the original recaps. FOR EXAMPLE, IF YOU USED A 0.01 Uf Reference, And The Meter Read 10 on The 0.1 Uf Range. IT Should Now Read 20.Now Switch Out The Divide-by-Two Function.
IF you are not doing so already, Change to a reference with a value equal to one of the Ranges (EG 1000PF, 0.0Luf, 0.1uf etc). Switch to the range equal to that value (ie the meter reads full-scale (100) when that capacitor is being measured.Switching in the x10 function should cause the meter indication to drop significantly.Adjust the 470 ohm trimpot so that the meteR Reads 10.Move Down One Range (EG FROM 0.01UF to 1000pf). The Meter Should Read 100 Again. IF it does not. Vary The 470 Ohm Trimpot Until It Does. That Completes The Calibration of The Capacitance Meter. Now Try Measuring Other Components To Confirm That The Measurements Are REASONABLE.
Be
WITH CARE. An Accuracy Of Five Percent or Better Should Be Possible On Most Ranges.
Use x10 switch to measure up 10uf. Use x0.5 switch for better readings on low value. "
Our other product:
