Search found 71 matches

by rosborne
Wed Aug 27, 2003 11:28 am
Forum: General Discussion
Topic: Measuring Resistance
Replies: 15
Views: 5543

Re: Measuring Resistance

That's what it should do. Your actually measuring the drop across the transistor if your reference is ground, which is the complement of hte voltage across the resistor under test. If you can use VCC as a reference it should work perfectly. Or you can do an easy software fix which is what I'd do. :-...
by rosborne
Tue Aug 26, 2003 3:45 pm
Forum: General Discussion
Topic: Measuring Resistance
Replies: 15
Views: 5543

Re: Measuring Resistance

Yes, this is not hard you need two transistors, prefferably matched, and two maybe three resistors counting the resistor under test. I'd rather draw but, will try with words to describe the circuit. 1. Two NPNs (Q1 and Q2) wired base to base and emitter to emitter. THis is ground 2. Q1:c to Q1:b is ...
by rosborne
Tue Aug 26, 2003 3:11 pm
Forum: General Discussion
Topic: Measuring Resistance
Replies: 15
Views: 5543

Re: Measuring Resistance

I'm assuming you meant 1V = 1000 ohms.
-Rick ;)
by rosborne
Fri Aug 22, 2003 1:09 pm
Forum: General Discussion
Topic: Diode Voltage multipliers
Replies: 10
Views: 3011

Re: Diode Voltage multipliers

Transformers should work backwards.
-Rick
by rosborne
Fri Aug 15, 2003 10:47 am
Forum: General Discussion
Topic: Need a circuit
Replies: 10
Views: 3341

Re: Need a circuit

I don't know how I double sent that. Sorry.
http://makeashorterlink.com/?T48424A95
is a link to a cheap place to post pics with readable closeups of some of the schematic. Can anyone advise me on how to better post pics like this?
Rick
by rosborne
Fri Aug 15, 2003 10:26 am
Forum: General Discussion
Topic: Need a circuit
Replies: 10
Views: 3341

Re: Need a circuit

I drew a partial schematic yesterday and here is a url for the picture. http://makeashorterlink.com/?X5B165A95 I don't get the url and image thing for this list. :-/ I had trouble figuring out how to post the picture. It's incomplete, but I think you'll get the idea. It's also never been simmed so t...
by rosborne
Fri Aug 15, 2003 10:25 am
Forum: General Discussion
Topic: Need a circuit
Replies: 10
Views: 3341

Re: Need a circuit

I drew a partial schematic yesterday and here is a url for the picture. http://makeashorterlink.com/?X5B165A95 I don't get the url and image thing for this list. :-/ I had trouble figuring out how to post the picture. It's incomplete, but I think you'll get the idea. It's also never been simmed so t...
by rosborne
Wed Aug 13, 2003 6:54 am
Forum: General Discussion
Topic: Need a circuit
Replies: 10
Views: 3341

Re: Need a circuit

My initial response is to suggest a 4:1 differential mux and some logic to drive LED's but I have a feeling your playing with analog signals.
-Rick
by rosborne
Mon Aug 04, 2003 12:00 pm
Forum: General Discussion
Topic: 5 sided semi enclosures
Replies: 2
Views: 701

5 sided semi enclosures

Looking for some almost boxes to mount to lab benches. I want to mount BNC barrels to one side for easy access to reference signals. The open side is where the cables would come in to connect to the barrels. They need to look kind of nice or I'd just get a 90 degree bracket and put the barrels in th...
by rosborne
Fri Aug 01, 2003 11:47 am
Forum: General Discussion
Topic: Any hints on how to buld pedometer?
Replies: 13
Views: 2500

Re: Any hints on how to buld pedometer?

I recently went to a seminar on GPS and just wanted to let you know that even a relatively inexpensive GPS ($150 US) is way better than 30 meter accuracy. I got this quote from Consumer reports. "For years, GPS units had an accuracy problem caused by Selective Availability (SA), an intentional degra...
by rosborne
Mon Jul 28, 2003 12:21 pm
Forum: General Discussion
Topic: electric meter rotor rpm vs power
Replies: 5
Views: 1170

Re: electric meter rotor rpm vs power

Sorry about that, I just realized that had nothing to do with your question. :-\
Rick
by rosborne
Mon Jul 28, 2003 12:20 pm
Forum: General Discussion
Topic: electric meter rotor rpm vs power
Replies: 5
Views: 1170

Re: electric meter rotor rpm vs power

I think you have to know what your load is and go from there or go from what you know your motor is drawing.<p>You might have a 1 HP motor (that's about 746 Watts), but you can't know whether the motor is suppling full load. The rpms ought to be about the same whether turning a full load or spinning...
by rosborne
Tue Jul 22, 2003 7:55 pm
Forum: General Discussion
Topic: Variable 10GHz attenuator needed.
Replies: 3
Views: 766

Re: Variable 10GHz attenuator needed.

Russ, The 10GHz signals comes off of a PCB through 2 SMA connectors to length matched coax cables. The signals are LVDS and are differentially coupled. 100 Ohms between the pair and 50 Ohms to ground. I'm currently wondering if the signal is properly coupled in the coax cables, I think not which may...
by rosborne
Mon Jul 21, 2003 12:42 pm
Forum: General Discussion
Topic: Variable 10GHz attenuator needed.
Replies: 3
Views: 766

Variable 10GHz attenuator needed.

Differential signal. Maybe 1 dB resolution. Idea's, anyone? Sidenote: How are optical attenuators made?
-Rick
by rosborne
Sun Jul 20, 2003 4:36 pm
Forum: General Discussion
Topic: Microwave Leakage Detector
Replies: 5
Views: 1295

Re: Microwave Leakage Detector

How strong is the EM source? Look up Branley Coherer. It was the first(?) EM wave detector in about 1890.
-Rick