07-26-2018, 06:51 PM
Hi Folks,
I mentioned needing a better capacitance meter in my thread on restoring the RCA 110K2. I eventually chose the Proster BM4070, which is available from several on-line sources. I paid $32.99. The primary motivation for acquiring this meter was to test small capacitors in the 100 pF - 1 nF range. My Fluke does a good job on the larger capacitances, but not the small values for critical RF circuit. This meter also makes measurement of resistance (200 Ohm to 20 MOhm ranges) and Inductance (200 uH to 20 H), and diode check but these functions have not yet been evaluated.
For the small calues of interest, stray capacitance associated with the circuitry and the meter leads can obviously affect the meter reading. There are a couple of ways to deal with this when using this instrument. Firstly, if the component can be removed, it may be inserted directly into sockets on the meter (remove the test leads as necessary as they will add capacitance). Where a part can only be disconnected at one end, the meter allows for the offset to be trimmed out. This works quite well, although one must be careful on the lowest ranges, as even small movements of the wires can affect the stray capacitance.
As an example of the functionality, I was having trouble with adjustment of the oscillator section on one shortwave band of the RCA. Testing showed that the caps I suspected first, and the trimmer were actually in specification according to the meter, but another 120 pF clamped, open style mica cap was between 10 and 15 pF low in value. Using the meter, I tested the available new replacement caps and selected the one closest to 120 pF. Problem found, and alignment issues solved.
Based on the experience so far, I would recommend this meter for hobby restoration use. When used thoughtfully, it easily met the purpose for which I bought it, providing enough precision in readings of small values to identify out of specification components and select the best fit from new parts. It is not auto-ranging, so a little attention is needed when taking measurements. It came supplied with a battery, a set of meter probes, a set of leads with clips and included a carrying case. When in use, the display can be tilted up to aid viewing.
I have no connection with the manufacturers or vendors of this instrument.
Ed
I mentioned needing a better capacitance meter in my thread on restoring the RCA 110K2. I eventually chose the Proster BM4070, which is available from several on-line sources. I paid $32.99. The primary motivation for acquiring this meter was to test small capacitors in the 100 pF - 1 nF range. My Fluke does a good job on the larger capacitances, but not the small values for critical RF circuit. This meter also makes measurement of resistance (200 Ohm to 20 MOhm ranges) and Inductance (200 uH to 20 H), and diode check but these functions have not yet been evaluated.
For the small calues of interest, stray capacitance associated with the circuitry and the meter leads can obviously affect the meter reading. There are a couple of ways to deal with this when using this instrument. Firstly, if the component can be removed, it may be inserted directly into sockets on the meter (remove the test leads as necessary as they will add capacitance). Where a part can only be disconnected at one end, the meter allows for the offset to be trimmed out. This works quite well, although one must be careful on the lowest ranges, as even small movements of the wires can affect the stray capacitance.
As an example of the functionality, I was having trouble with adjustment of the oscillator section on one shortwave band of the RCA. Testing showed that the caps I suspected first, and the trimmer were actually in specification according to the meter, but another 120 pF clamped, open style mica cap was between 10 and 15 pF low in value. Using the meter, I tested the available new replacement caps and selected the one closest to 120 pF. Problem found, and alignment issues solved.
Based on the experience so far, I would recommend this meter for hobby restoration use. When used thoughtfully, it easily met the purpose for which I bought it, providing enough precision in readings of small values to identify out of specification components and select the best fit from new parts. It is not auto-ranging, so a little attention is needed when taking measurements. It came supplied with a battery, a set of meter probes, a set of leads with clips and included a carrying case. When in use, the display can be tilted up to aid viewing.
I have no connection with the manufacturers or vendors of this instrument.
Ed
I don't hold with furniture that talks.
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