Cragon MF47 million meter, MF47 meter
Keywords: MF47, multimeter
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Author: Xie Hongwan
First, use the MF47 million menu problem 1. When measuring the light emitting diode, only the positive and reverse resistance values can be measured, and it cannot be luminated, not intuitive.
Due to the first four electrical barriers (R × L, R × L0, R × L00, R × 1K) of the MF47 million meter, the power supply voltage is only 1.5V, and the light-emitting diode door is 1.6V; the fifth electric stop (R × L0K) The output current is only dozens of μA, and the light-emitting diode operating current is generally necessary to digital MA, so the light-emitting diode can not be significantly illuminated when using each electrical blocking measurement, and it is not intuitive. Time to determine the pin arrangement of the multi-digital tube.
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2. When the common triode HFE is measured, the test holder of the meter does not match the common triode package size, the test is very inconvenient, specifically: 1 spacing problem, an existing MF47 million HFE test seat jack spacing is about 5mm, and Common 90 series (using T0-92B packages) and other small power triode tubes are only 1.27mm, and the tube of the triode needs to be bent. 2 Sequential problems A transistor such as C1815, C1015, the pin arrangement order is ECB and multimeter test holder for EBC, and there is two pin to cross. 3 Diameter issues One medium power tube, the pin is too thick to directly insert the existing test holder. The above problems are especially inconvenient for bulk testing.
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Second, the improved method is for the above situation, and the existing MF47 million menu is improved. Also suitable for other similar pointer-type menu.
1. Improve power blocking power. The principle circuit is shown below, increasing a battery and a conversion switch, making its power supply at two voltages between 1.5V and 3V, for the former for the measurement of the original table, does not affect the design and use of the original multimeter, Used to measure light emitting diodes and digital tubes. During the improvement process, due to the limitations of space in the case, the original No. 2 battery is changed to two-five batteries (fixed battery case fixed), and the case after the case rear box is installed.
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2. Making a triode HFE test holder. It is often found in various packaged triodes and related materials, with their pinpage spacing with a scale, found that there are four types of common spacings, 1.27mm, 2.0mm, 2.54mm, 5.08mm, because there is no current holder Instead of replacing it with a row, 5.08mm is not bought, I do one. Then use the Prote199se to draw a small circuit board by the manufacturer, and the new triode is installed on the board. After the original multimeter HFE test, it is possible to measure the magnification of various three-pole in the market.
After the production, the HFE of the high-power triode was small (generally not more than 20), and the multimeter HFE gear is mainly used to measure the magnification of small power triodes, and the magnification scale is large, about 50 to 300 times, for The high-power triode HFE was measured and a small range HFE gear was designed.
3. Further improvement. After the above two modifications were finished, it was further investigated that the improved multimeter can also measure the good or bad of the porcelain capacitance of small to PF. So some of the boards for measuring the quality of the capacitor and the light emitting diode. The active material is as shown in the figure. Printed circuit board is shown below.
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