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Re: [TCML] Terry Filter Resistors
Hi,
today I calculated and measured a tapped 40W / 1.2kOhm enamelled resistor I
had laying around. The label says:
B83004
1.2kOhm 5%
40W-3.0
Googling the manufacturer gives CTS (who is that?) or "blank". The tapped
zone allows to count turns. A picture can be had at:
http://twfpowerelectronics.com/~kurt/Downloads/Drahtwid_1.2k40W_k.JPG
Looking at it like a TC secondary, the relevant data become:
total turns: 226
Coil diameter: ~1.25 cm
Coil length: ~7.8 cm
Wire diameter: ~0.26 mm
Space between turns: 0.085 mm
Length of wire: 8.9 m
Calculated values:
DC-Inductace (Lundin): 94.4 uH (micro Henries)
Medhurst Capacitance: 1.17 pF
Approximate resonance: 15.125 MHz (which will not be observed, 'cause of the
R...)
I tried to measure the resistor with my ESCORT ELC-131D LCR-meter, which
should be an automatic bridge type meter, see:
http://www.arronet.de/escort.htm
http://www.otdl.com/131d.pdf (for specifications)
L measurement:
The bridge seems not able to home-in to a stable value, at such a low L/R
ratio. At 1kHz the values oscillate between about 300uH to 400uH; at 120Hz
they vary between about 3mH to 4mH indefinitely.
R measurement:
The meter shows a correct value of 1.25kOhm.
Well, the meter is not suited for this kind of measurements, but the
calculations seem plausible. While the resistor is not 1kOhm/100W Ohmite, I
expect, the relations beeing of similar kind.
Best regards, Kurt
piranha wrote:
Hi,
Better LCR meters read "Q" at 1000 Hz. 50mH at 1000Hz is .314 ohms.
Sort of hard to see with 1000 ohms in series... Your going to have to
pump MHz through there to see the inductive effects... The 27XT is a
wonderful meter and I use mine almost every day :D But it is designed
to measure the inductance of grandma's old tube TV's inductors, not
complex things...
http://www.dtv.gov/
I have the digital signal generators and all if some "experiment"
needs to be done. Time is short these days, but if a question needs
an answer, I will make it so...
Best Regards,
Terry
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