Fluke 77 IV Question

[Sepp]

Hi,
Years ago before the debut of microprocessors, I worked in the field of electronics and electro-mechanical Teletype equipment, got into administration and now have the bug again.  I recently purchased a Fluke 77 IV and need some help please.
Since the purchase, I first read the manuals and watched a lot of videos to get more exposure to Fluke products and more importantly check my new toy to be sure it is doing what it is suppose to.   

(I started out with analog Simpson's so please be patient with me.)

Q1-   I took a reading of my household current (US circa 120VAC) and the meter beeped a couple of times, indicating the meter detected new values.  However, when I pressed the MAX/MIN/AVG button I got the following values:
MAX-126
MIN-0
AVG- The meter started at 51 and began a slow and sequential count down.   

Question:  Why did AVG not yield the average of the High and Low readings?. 


Q2- Is there a source I can go to that would have a check list of checks on the Fluke 77 IV or similiar model.

Any other advise would be greatly appreciated.

Thanks.

[TechJunkie]

Hello Sepp,

 I have several Fluke products but not a 77 IV. I believe Autoranging is disabled during the Min/Max/AVG function. You may want to setup the meter in the proper manual mode range with the desired function first before entering Min/Max mode. This might help.

Flukes website has some very informative whitepapers. You might want to check out some of these. Hope this helps!

Eric

[ProBang2]

Q1-   I took a reading of my household current (US circa 120VAC) and the meter beeped a couple of times, indicating the meter detected new values.  However, when I pressed the MAX/MIN/AVG button I got the following values:
MAX-126
MIN-0
AVG- The meter started at 51 and began a slow and sequential count down.   

Question:  Why did AVG not yield the average of the High and Low readings?.

It made a perfect job. The Fluke77 just works well.
The AVG display is only correct  while the probes are connected to the mains.
Donīt forget: The multimeter shows the AVG over time and itīs taking 3 readings per second.

A simplified example:

Connecting the probes and activating Min/Max.

1st  reading  is  130V. Result: Max=130 Min=130 AVG=130
2nd reading  is  110V. Result: Max=130 Min=110 AVG=120 (as expected...)

Disconnecting the probes. The multimeter is still working and is taking readings.

3rd reading is now 0V. Result: Max=130 Min=0.0 AVG= 80 (Yes! Immediately Min=0. What else?)
4th reading again  0V. Result: Max=130 Min=0.0 AVG= 60
5th reading again  0V. Result: Max=130 Min=0.0 AVG= 48
and so on...

What happened?
The AVG is determined through the addition of the voltage measurements divided by the numbers of readings.
(It does not add Max and Min, and then divides the sum by 2, as some other meters do.)

Example:

20 seconds (=60 readings) measured 50 V (=3000)
10 seconds (=30 readings) measured 35 V (=1050)
30 seconds (=90 readings) measured 15 V (=1350)
---------------------------------------------------------
measurements (3000+1050+1350)= 5400
number of readings (60 + 30 + 90)= 180
AVG = 5400/180 = 30

If the probes were then disconnected
20 seconds (=60 readings) later the result is:
AVG = 5400/240 = 22.5
10 further seconds later:
AVG = 5400/270 = 20
and so on...
thatīs your countdown.

(BTW: Activating the Min/Max/Avg-function before connecting the leads has the same effect: It only increases the number of measurements, not the sum of the measurements.)

This kind of determination the average is very useful and usable.

Iīm hoping, that Iīm not sounding like yoda and you could get it.

Greetings,


Hartmut