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How much does it cost to calibrate a digital multimeter?
How is
this done?
cen-tech 90899 98025
Evelin Wheeler appeal for help.
Battery tester comparisons.
#3 appears to work with 9v
#5 [not numbered yet - we return them if they are not within spec. Harbor Freight employee wrote reason #2 sucessor was bad and issued #2] appears not to work. #2 gets about the same value.
#4 appears to work with NIMH AA.
#5 doesn't appear to work the NIMH AA either.
#1 appears to have problem with 9v.
Fuse tested good.
Whoops! This may be the reason #1 is over-range with 9v.
We, if we recall correct, think #1 worked fine testing 9v NIMH several days ago.
Tuesday April 13, 2010
All eight multimeters poised to measure 2k ohm precision resistor.
Fourth free 9 LED [blue] obtained when we bought pack of 4 9v batteries with 20% off coupon at Harbor Freight.
2 K ohm precision resistor and test clips.
The $1.99 CEN-TECHs look to perform well.
They are using direct chip attach technology.
Since we are using these meters to monitor solar panel peformance, we want to be careful about their accuracy.
The Soar failing miserably agree with the CEN-TECHs measuring voltage was a bad shock.
Monday April 12, 2010. Battery charging function onboth the 98025 [red on/off button and 98099 [yellow on/off button] both models reads 1.5v(4.0mA) 9v(25mA).
Yellow button read about 26 mA on 9v batteries. Red button about 9.45 mA.
Yellow button read about 3.5 mA on rechargable AA 1 and 2. Red button about 1.24 mA on same batteries.
We compared meters 2 and 5 [red] and 1 and 3 [yellow]. Both were consistent so we conclude the 98025 may not work for measuring battery under advertised 370 m ohm load.
We measured two DURACELL AA batteries with CEN-TECH #1: both measured
1.62 volts.
The soar 1.38 v.
Next two Thunderbolt AA measured
with CEN-TECH #1: 1.63 volts each. The soar: 1.39 v each.
Oh
dear.
Battery # 1 and 4 out of charger at about 10:30. Red CEN-TECH
removed fom outside open circuit solar volatage measurement.
Red CEN-TECH measures # 1 at 10.10 volts, # 4 at 10:14 v.
Soar measures # 1 at 8.63 volts, # 4 at 8:66 v.
We may have a serious soar accuracy problem which propogates back though
this page.
10.10 - 8.63 = 1.47 and 10.14 - 8.66 = 1.48. Not good.
Almost the last photo.
Solar panels voltage is amazing in that
even in dim light voltage is high.
Ground to load disconnected. Note panel voltage and LED illumination.
Here's the final photo of the window setup.
Meter # 2 is measuring the IR drop across the 2k ohm LED
resisitor.
Note LED is ON.
Here's solar panel number two identified with blue tape.
We'll move solar generated electricty project [The Phoenix project] to the service cart.
Energy efficient Better Homes and Gardens plan roof overhang now leave the panel in a perpetual shadow.
Meter #1 Thunderbolt battery measured 6.12 v. Thunderbolt replacemen measured 8.39 v.
Harbor Freight AA Thunderbolt batteries are measuring about 1.39 volt.
Coupon for $2.00 saving received in Sunday paper.
November 23, 2009 manufacture date?
Two Duracell AA in pack seen above measure 1.37 volts!
# 4
contains a Gaoli measuring 4.29 v. Thunderbolt replacement measure 8.35 v.
April 6, 2010.
$1.99 meters appear to read high voltage when batteries begin to fail. April 6, 2010 11:10.
#4, 1, and yellow are all measuring IR drop across 50 ohm resisitor.
# 3 is measuring panel voltage. Big CEN-TECH is measuring
current.
# 2 is measuring IR drop across LED. Note carefully that the
LED is lit! Barely.
Battery # 2 [over?] charged on Tuesday April 6, 2010 08:50; 8.76 volts.
Big CEN-TECH measuring current died Monday April 5, 2010. Battery # 2 removed. It measures 1.61.volts.
Battery #3 measuring 8.16 volts replaces # 2 in bit CEN-TECH.
When the big CEN-TECH was removed from the circuit, the panel voltage soared to more than 17 volts. The green LED was bright.
When the big CEN-TECH was reinserted in the circuit, the panel voltage dropped to less than one volt and the LED went out.
Observing the meters reveals that solar generated power is unstable both in voltage and current. The meters apparently sample about 2.5 time a second.
Meter values are always changing. Here's a video.
The top little red CEN-TECH is measuring panel voltage.
Three are measuring IR drop across the 50 ohm load resistor.
#2, reading about 1.88 volts, is measuring voltage drop across the LED.
Little red $1.99 CEN-TECH # 3 died Sunday April 4, 2010. Dead battery we assume. Gaoli measured 5.63 v.
# 3 is ITEM 90899 with yellow on/off switch.
Note fuse holder and direct chip attach technology for the microcontroller.
Battery # 3 emerged from charger. 8.54 v.
Battery # 3 in Big CEN-TECH died Tuesday March 30. It measures 1.66 v.
Battery #2 now measures 8.06 v. It is replaceing battery #3.
Battery # 3 goes into charger for at least 18 hour charge.
We are getting a clearer picture of why we abandon NIMH batteries for camera use several years ago.
High voltage reading were observed on yellow CEN-TECH after the low
battery icon appeared. Same for red CEN-TECH #2.
#2 is ITEM 98025 which
is different from our other #1, 3, and 4.
We're replacing the orginal battery with Harbor Frieght Thunderblot magnum alkaline with Exp.Date of 10-2012. Thunderbolt measure 8.25 volts.
Dig direct chip attach technology for the microcontroller! An 80C51 variant?
The microcontrolller die is attached directly to the board. With lead packaging little wires are welded on to the die and pads.
Note that the fuse is soldered in.
Colorful battery 6.11 volts.
Yellow CEN-TECH battery was replaced with NIMH #4. Yellow CEN-TECH
measurement were high. See.
#2 out of charger on Thursday
As soon as battery was replaced it now agrees with 1, 2 and 4.
Note that CEN-TECH #2 low-battery icon is displayed.
March 24, 2010 08:00. #2 measure 10.02 v.
#4 out of charger, 10.20 v Wednesday March 24, 2010 11:00. #2 in charger.
Big CEN-TECH measuring current quit. Battery #2 in it measures 2.92 v Wednesday March 24, 2010.
Battery #3 measure 9.67 is inserted in Big CEN-TECH.
Little
yellow CEN-TECH has been showing low battery icon for several days but is still
working
Battery #3 no load voltage has declined to 9.73!
Battery #4
entered service at 9.06 v. #4 is in charger.
20% off coupon plus free LED flashlight.
Battery #3 charged to 10.22 v measued at 07:08 Tuesday March 23, 2010.
Soar with battery #3 quit Sunday March 21, 2010. Monday March 22, 2010 it measured 2.87 v.
#1 is placed into Soar, #3 into the charger.
#1 200 mha 9v is out of the charger measuring 10.24 v on Friday March19, 2010 15:24.
Thursday both Soar and Big CEN-TECH batteries failed. They were replaced with 9 v 200 mah NIMH batteries #2 and #3. #1 was placed in the charger at 17:00 for 18 hour charge.
Wednesday March 10, 2010 Soar Harbor Freight alkaline battery failed.
9 V 200 mah battery1 measures 9.50 volts with $1.99 small red CEN-TECH 2. Battery 2 measures 9.52 volts.
#2 placed in Soar.
We bought our charger for use on Harbor Freight standard NiMH AA for use in a digital camera.
NiMH batteries nominal voltage level is 1.2 v. They did not work well at all because they depleted very quickly.
So we've been using Harbor Freight Alkaline batteries which we buy 25 for about $5 on sale.
Harbor Freight introduced high capacity NiMH batteries which we are going to test.
First we charged them.
We waited about 40 hours for the LEDs to go out. They didn't.
So we decided to read the instructions.
Oh dear.
We googled overcharge nimh battery damage.
Nickel-metal hydride battery.
Little red CEN-TECH 2 was removed from the solar panel project.
Little red CEN-TECH 2 measured battery 1 9.89 V and 2 9.85 volts.
We plan to use these to power the multimeters in our solar panel project. We well records how many hours they last.
EE&T January/February magazine arrived Saturday March 6, 2010.
A lesson in quick-and-dirty solar charging we found valuable for its realistic assessment.
