Fluke 117 DC Volts Problem - Page 1
Forum section: electronics / testgear

author: TonyMitchell
author_rank: Newbie
timestamp: April 09, 2019, 05:10:22 pm
content: Hi, newbie here.My 117 is behaving peculiarly when set to DC volts.I have a known 22V DC source, which the 117 measures correctly using the LoZ Auto-V settingHowever when set to DC volts, the Auto mode, it scales to 600 and displays OL with the bar graph fully populatedSimilarly, when set to Manual, irrespective of whether range is set to 6, 60 or 600, the display is OL and the bar graph fully populated (which should only be in this state when set to 6, when connected to a 22V source)Any ideas?

author: retiredcaps
author_rank: Super Contributor
timestamp: April 09, 2019, 06:38:03 pm
content: If you measure a 1.5AA cell, what do you get with the meter set on DCV auto and 6 manual range? Is it 1.5 or 0L?What is your 22V source?

author: TonyMitchell
author_rank: Newbie
timestamp: April 09, 2019, 07:12:54 pm
content: Hi retiredcaps,A 1.5V cell reads correctly on both the numerics and bar graph, in DC Auto and all 3 manual ranges.The 22V source is a fly killer. It reads correctly on LoZ Auto-V but I cannot get a meaningful reading when set to DCV, either auto or manual

author: retiredcaps
author_rank: Super Contributor
timestamp: April 09, 2019, 07:49:00 pm
content: Quote from: TonyMitchell on April 09, 2019, 07:12:54 pmLink to product or manual or more details?

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2019, 08:01:37 pm
content: Quote from: TonyMitchell on April 09, 2019, 07:12:54 pmMaybe it's AC.

author: JDubU
author_rank: Frequent Contributor
timestamp: April 09, 2019, 08:04:07 pm
content: Not going to zap a fly with 22V.Maybe the 22V source has some high Z, high voltage superimposed on it? The low Z input mode of the Fluke 117 might be dropping the superimposed high voltage down close to zero, via the high z of its source.

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2019, 08:11:18 pm
content: Quote from: JDubU on April 09, 2019, 08:04:07 pmNope, usually they're thousands of volts. I wouldn't touch one with a multimeter.

author: TonyMitchell
author_rank: Newbie
timestamp: April 09, 2019, 08:59:14 pm
content: Quote from: Fungus on April 09, 2019, 08:01:37 pmIt is DC, powered by 2 x 1.5V cellsIf it was AC, it wouldn't measureDCVolts on the AUTO-V setting.

author: TonyMitchell
author_rank: Newbie
timestamp: April 09, 2019, 09:02:30 pm
content: Quote from: Fungus on April 09, 2019, 08:11:18 pmIt is a handheld "tennis racquet" style thing. It is 22V and it kills small flies and sufficiently disables larger flies & wasps.

author: JDubU
author_rank: Frequent Contributor
timestamp: April 09, 2019, 09:16:35 pm
content: From Wikipedia (https://en.wikipedia.org/wiki/Fly-killing_device):"Electric flyswatters (sometimes called mosquito bats, racket zappers, or zap rackets) are hand-held devices that resemble badminton rackets or tennis rackets, which became popular worldwide in the late 1990s.[citation needed] US Patent 5,519,963 was awarded to Taiwanese inventor Tsao-i Shih in 1996 for such a device. The handle contains a battery-powered high-voltage generator. The circuit is composed of an electronic oscillator, a step-up transformer and a voltage multiplier, similar to the circuit in an electroshock weapon or stun gun, but with much lower power.The grid of the flyswatter is electrically charged to a voltage of between500 and 1500 volts(V) of direct current, activated by pressing and holding a button. When the electrically conductive body of a fly nearly bridges the gap between electrodes, a spark jumps through the fly. A capacitor attached to the electrodes discharges during the spark, and this initial discharge usually stuns or kills the fly. If the button is still pressed, the continuous current will roast and kill the fly. Many flyswatters have a three-layer grid to prevent people from touching both electrodes. The outermost grids or rods are at the same electrical potential, and are open enough to allow an insect to contact the inner charged grid.Most electric flyswatters conform to electrical safety standards for humans:a limit on the charge stored in the capacitor: a discharge of less than 45 microcoulombs (µC) is considered safe, even in the unlikely scenario that the current from a flyswatter would be flowing from one arm to the other arm, partly through the heart. This means that the capacitor of a 1000 V flyswatter should be less than 45 nanofarads (nF). Due to this precaution for humans, the initial shock is usually inadequate to kill flies, but will stun them for long enough that they can be disposed of.A limit on the current after the initial discharge: the maximal continuous current of most flyswatters is less than 5 milliamps (mA). This current is safe, even when flowing from one arm to the other arm of a human.An advantage over conventional flyswatters is that the electrical models do not have to mechanically crush the fly against a hard surface to kill it, avoiding the smeared mess this can create. Also, the electrical grid can be relatively open, reducing air resistance and a rush of air that often deflects smaller insects around conventional swatters. Because of this, electric swatters can also be very effective in killing airborne mosquitos and "no-see-ums"."

author: TonyMitchell
author_rank: Newbie
timestamp: April 09, 2019, 09:22:20 pm
content: Quote from: JDubU on April 09, 2019, 08:04:07 pmThis seems to be a reasonable explanation, since:I measured 13 x 1.5V cells in series, the 117 gives good readings circa 21V in all modes (LoZ AUTO-V, DCV manual, DCV auto)I have also successfully measured 112V, 270V and 546V in DC manual and DC auto modes to 0.1V accuracy, using my MFT as the DCV source

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2019, 06:14:01 am
content: Quote from: TonyMitchell on April 09, 2019, 08:59:14 pmIt won't if it's 50Hz bit it might if it was high enough frequency.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 10, 2019, 11:54:05 pm
content: Quote from: TonyMitchell on April 09, 2019, 07:12:54 pmAnother classic! A lesser meter may have been done in but I have had pretty good luck with Fluke branded products.

author: Electro Detective
author_rank: Super Contributor
timestamp: April 11, 2019, 12:42:22 am
content: If the 117 still reads 1.5 or 1.6v with a healthy/new battery in both DC and Low Z mode =it's good news and also means 'cease and desist' NOWbefore an input protection fail comes a knockin, and or a freak arc/zap eventually hops to where it shouldn'tKnock up a 100:1 voltage divider or reducer string of resistors for less than a dollarPlease ignore my comment if shopping for another 117 is no problem