QM1323 Multi meter -What is the red light built in used for ?

[squishy36]

There are a variety of DMMs on the market that include non-contact voltage sensors. Maybe that's what you got, but it's from a brain-damaged manufacturer that doesn't know how to document its product.

 

[Reloadron]

I found this:

The flickering LED at the top of the meter is a non-contact voltage detector (NCV).
When you place the top of the meter near live mains cabling the LED lights (or flickers). It basically detects AC provided the frequency isn't excessively high. It's similar to those little pocket/pen devices.
Note the LED will flicker even when the multimeter is switched to off. Don't store the meter near mains cables on your desk otherwise it could flatten the battery.

And a few other references that say the same. Why it would not be documented in the manual I have no clue?

The quote was taken from here.

Ron

 

[Fixmycom]

Well I have a similar prob - very annoying - the LED/neon pulse when on or off at about 1 hz - if i approach a AC live wire it speeds up such that when i rest the meter finally against the wire it appears to stay on without pulsing, although i suspect it is actual pulsing at 50 hz. I have taken it into the middle of a paddock to remove all chance of it being supersensitive to ac frequency but it still pulses at about 1 hz. I am going to take it to town tomorrow to get it away from where i live which is about 1km from Mount Moonbil TV Transmitter - its 250.00kw for frequencies from 543.500 Mhz to 606.500 Mhz for the various channels, as well as optus and telstra towers so we maybe frequency riddled. - god knows how it could be effecting the multimeter, but I am out of things to try - taking the battery out after using it is such a pain. If i don't it goes flat in a couple of weeks. Jaycar, where i got it are unable to suggest anything other than replacement after they check it out, if i can find the docket. All in all a pain.

 

[Phocks]

I have one of these Digitech QM1323 Multimeters brought in Nov 2013 from Jaycar, who remain silent to my emailed questions re the red led/neon/lamp. My instructions make no mention of the light and I find it flashes at about 30 second intervals when left on our kitchen table and or on my desk at work. A tap to the meter brings the light up for about half a second both meter on or off. Holding the meter near any 240volt AC source (and held still) the red light comes on with meter off or on in any of its seven test positions. The red light stays on the entire time meter is held near 240volt AC source (Test period upto 30 seconds).

 

[dr pepper]

I have a pocket torch by fluke, it has a similar led, well 2 red and blue, they are as allready mentioned part of a non contact voltage detector.
It probably responds to movement due to the static created, I check mine is working before I use it by rubbing it on my sleeve.

 

[David Morton]

I have had this meter for 3 years and until a few days ago didn't know it had non-contact voltage sensing; I was actually looking for an online manual as a refresher. Two things happened, I found a scan of the manual on a backup disk; and it talks (albeit vaguely) about non-contact tests; so I had a play. Yes, mine normally blinks every few seconds but does go solid red when near a mains lead, even if off. I figure it blinks to inform me the non-contact sensor is working, like a standby device. The second thing I found was the disappointment and so much negativity on this forum. I enjoyed playing with my meter to find out about the non-contact sensing. I wish many of you would also experiment, it's the best way to learn. Now, there is no copyright mentioned in the manual, so I'll try and upload it.

 

[b.james]

In fact it picks up any Electrical frequency activity near the meter . Put it next to a power line at 50 Hz and it lights up at about 3 inches away

 

[Afterburn]

I have one of these QM1323 MMś and the red lamp flashes with no apparently consistent reason. Does anyone know what its for ?


Cat III Multimeter with Temperature


• Data hold
• Relative measurement
• Case included

A budget-priced meter with everything you need - capacitance, temperature and 10A on AC and DC, compact and light weight with rugged moulded case.

Specifications

Category: Cat III 600V
Display: 4000 count
Basic accuracy: 1%
DC voltage: 600V
AC voltage: 600V
DC current: 10A
AC current: 10A
Resistance: 40Mohms
Temperature: -50 - 760°C (-4 - 1400°F)
Capacitance: 40µF
Frequency: 5MHz
Ave/RMS: True RMS
Dimensions: 137(H) x 65(W) x 35(D)mm

I bought one of these meters for its temperature capability and at first thought it a camera. Ha, ha! Moving the meter, bumping it and waving a hand close to the screen caused the LED or neon to flash. Holding it close to a power point or light switch made it light continuously. I then thought of it as a high volts detector - the high volts being normal household voltage.
The manual does not indicate a purpose for the 'indicator'. The battery in my meter was flat when I purchased it. It didn't indicate until the battery was replaced.
This leads me to believe that the 'indicator' is 'in-circuit' all the time and cannot be turned off. This would explain the dead battery in my meter. How long did it sit on a shelf? I bought it in March or April of this year - 2014.

In support of this conclusion: I paste the following:

It is not the same meter but that capability is available. Bumping, moving and proximity to the meter may trigger the sense circuit.

 

[alec_t]

A daft idea having a meter which operates even when switched off. If I had one methinks I'd modify it to have the LED (and hopefully the voltaage-detect circuit) switchable.

 

[Afterburn]

My only thought here is that placing an on and off switch through the casing could effect the CAT III-600V rating. This is not an excuse, only a suggestion. Then the circuit could be activated ONCE the rotary switch applies power from the battery?

 

[Nigel Goodwin]

A daft idea having a meter which operates even when switched off. If I had one methinks I'd modify it to have the LED (and hopefully the voltaage-detect circuit) switchable.

As it's entirely passive what would be the point? (and it's presumably a neon, not an LED )

I presume it's just the same as the mains detect 'pens' you can buy?.

 

[audioguru]

One of our members here posted a thread about a "ghost detector" (or static electricity detector) that used an extremely high input resistance of a Fet to turn on an LED and when the LED was not lighted then it had almost no current drawn from its battery.
This meter that lights its LED even when it is switched off could easily kill its battery if it is stored near an electrical outlet like my multimeter has been for a few years.

 

[alec_t]

As it's entirely passive what would be the point?

I don't see any mention of it being passive?

A tap to the meter brings the light up for about half a second both meter on or off.

I'm struggling to see how you could manage that with either a passive circuit or a neon.

presumably a neon, not an LED

Maybe; but posts above have mentioned LED.

 

[Afterburn]

The above is from the operating instructions for the QM1323 Digitech meter. It calls the item a 'detector light'. It looks like the lens of a LED.

A LED draws about 20mA when conducting and has a forward voltage drop of 1.2 volts which can be supplied by the battery.

A neon draws much less current but requires far more voltage to trigger and is not uni-directional. It does not have a diode action.

 

[audioguru]

It says, "Non-contact" then explains, "Touch the probe tip to the hot conductor". That is not non-contact! My neon light bulb also glows when I DOO DAT.
My neon light bulb glows when it is very close to (but not touching) high voltage.

 

[Afterburn]

I didn't write the manual for this meter. You are correct. It is indicating real contact with the power socket and hot wire. It says to use a single probe... using it as an antenna.

It also means that the probe can make contact with the insulated hot wire without metal on metal contact and indicate the presence of voltage. The indication is only meaningful when it remains lit while in close proximity. I hold the meter itself close to power points, light switches and have not used a probe for this.

Note one describes the nature of a twisted conductor sheathed cable and warns that the position of the hot wire varies along its length. In some places the hot wire is closest to the viewed surface and at others, furthest away. That is the meaning of moving the probe along the length of cord.

Can you please give more information on your neon light bulb sensor? The only device I am familiar with is a pen like device with exposed metal. It was placed onto a hot wire and current flowed through the neon and your body to ground and illuminated when high voltage was present. These were deemed illegal in industry. Some people have low body resistance, a fault can occur and the neon short out...

 

[Nigel Goodwin]

Some people have low body resistance, a fault can occur and the neon short out...

There's a high value resistor in series with the neon, so it doesn't matter if it shorts, or if you have low body resistance.

They are still freely available here, and I've never heard any suggestion they had been considered a safety risk?.

 

[Afterburn]

Please consider my statement - 'The only device I am familiar with is a pen like device with exposed metal. It was placed onto a hot wire and current flowed through the neon and your body to ground and illuminated when high voltage was present.'

If it has 'a high value resistor in series with the neon', other than the body's resistance, then there is no need to reply in such a way. This is my experience of such a device.

Are you Scrooge McDuck???

 

[audioguru]

I am Scrooge McDuck. Nigel is the Super Moderator.
I do not have a pen device with a neon bulb but I have two neon voltage testers. They are made for testing the presence of 90V to 600V AC or DC and have a 120k (I guess) resistor in series with the neon bulb to limit the current.
They have two short metal probes. If I hold one probe in my hand, I am not grounded and I touch the other probe to the 120VAC live conductor then the space between the posts inside the bulb dimly lights.
I didn't see what happens (tingle or ZAP?) if I do it when I am grounded. Only one post inside the bulb glows when testing high voltage DC and both light with high voltage AC.

I have seen electricians use their hand (only one hand so the electricity does not go through their heart) to test for 120VAC. They do it all the time. I never tried it.

 

[Nigel Goodwin]

I have seen electricians use their hand (only one hand so the electricity does not go through their heart) to test for 120VAC. They do it all the time. I never tried it.

Perfectly valid with 240V as well - PRESUMING YOU KNOW EXACTLY WHAT YOU'RE DOING, AND WHY

However, 'using their hand' is a bit vague - personally I would use the back of a finger.