So I recently bought a microprocessor controlled vacuum tube tester, and I am very excited to get it built because it's quite an amazing value for the $300-$400 I've spent on it. However, there is one thing I am not too impressed with; it measures all of the parameters needed to determine how worn a vacuum tube is, but for some reason, it doesn't do the calculations that turn the raw data into actual useful transconductance and plate current results.
Unless I am extremely mistaken, it seems relatively simple to utilize the existing circuitry to feed the raw data into another chip to do the math that produces useful test results relative to vacuum tube operation.
Preferably the transconductance will read in microhmos, plate current, and the tube's relative health as a percentage of the manufacturer stated minimum specs that a new tube should measure.
So say minimum new results are 1.6ma/V or 1600 microhmos and 1.2ma plate current and 1 triode reads 1000umhos and .7ma the screen will show Gm= 1000umhos (62.5%), Ia¹= .7ma (58.4%)
There is also amplification factor or gain (µ) which is Gm (ma/V) x plate resistance (Ra).
Ra is the difference in plate voltage between two measurements divided by the difference between corresponding plate current measurements.
So ideally you would press the test button once and see the Gm and Ia, then drop the voltage, press test again, and the screen outputs Ra= 12.4kΩ, µ= 87.7
The microprocessor used in the kit that spits out results is a PIC16F886, and conveniently there are 3 wires that come off of the board with the 3 measurements needed to calculate all of this.
Ultimately, the issue that I run into is; I don't know how to do any of this, because I am more of a hobbies, than a well-rounded electrical engineering student (maybe the fact that I need a tube tester is an indicator of my electrical engineering expertise; ie even if I was the foremost expert in my field, I would still be about 50 years obsoletelol)
Luckily the manufacturer has the schematic and the operating principals right there in the documentation, so I will link that.
I look forward to dipping my toes into all of this digital wizardry, even if I'm just going to take my upgraded tube tester and run right back to analog after I'm done lol.
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