MR-9 adapter voltage question

[Bwbuff]

Is the MR-9 adapter only accept SR43 battery according to the description from the packaging ? I don't have any SR43 to test, I had tried the LR44 and SR44w without the adapter the voltage shows 1.56v and 1.59v. With the adapter , the voltage did not drop to 1.35v as expected, it shows 1.51v and 1.52v respectively. I tried both adapters , the results are the same . These are the Kanto camera MR-9 from Japan. Also I tried the Zinc air 1.35 V with/without the adapter, the voltage remains 1.35 volt.
Any idea why ? thank you.

 

[blee1996]

You can try adding a 10K resistor to the output of MR-9 and measure again. The alkaline battery and MR-9 might behave differently with or without load. You were measuring open-circuit voltage, and the values seem correct.

 

[Pieter12]

After reading the description of the adapter, it seems it is designed to work just with the specified SR43 battery.

 

[reddesert]

These adapters contain a diode (probably a Schottky diode), whose voltage drop depends on the current draw (like all diodes). At nearly zero load, they'll have nearly zero drop. So as blee1996 suggested, you are likely to get misleading results testing it without a load.

An SR43 battery is a silver oxide battery (equivalent to #386) that is 11.6 x 4.2mm.

An SR44 battery is a silver oxide battery (equivalent to #357) that is 11.6 x 5.4mm.

You can get these specs from any battery maker, like exellbattery.com. I don't have this exact MR-9 adapter, but I am certain that the difference between SR43 and SR44 is about whether the larger battery physically fits in your camera/meter when it's sitting in the adapter. If it fits, just try using the camera.

 

[dynachrome]

I found that with an MR-9 adapter and an MS-76 (or equivalent size battery), with some cameras, the battery cover would stick out and the bottom of the camera would not sit flush on a flat surface. With these cameras I used the slimmer 386 battery instead. The 386, being smaller, may be exhausted slightly sooner but is sometimes a better fit.

 

[wiltw]

There are some so-called 'MR-9' adapters sold on the market which are NOT Voltage conversion capable, but rely upon the use of 1.35V air cells...typiically thses have a hole in them to admit air to the cell. Do you have one of these imposter MR-9?

 

[Bwbuff]

There are some so-called 'MR-9' adapters sold on the market which are NOT Voltage conversion capable, but rely upon the use of 1.35V air cells...typiically thses have a hole in them to admit air to the cell. Do you have one of these imposter MR-9?

The ones I have has a tiny diode at the bottom .

 

[Bwbuff]

These adapters contain a diode (probably a Schottky diode), whose voltage drop depends on the current draw (like all diodes). At nearly zero load, they'll have nearly zero drop. So as blee1996 suggested, you are likely to get misleading results testing it without a load.

An SR43 battery is a silver oxide battery (equivalent to #386) that is 11.6 x 4.2mm.

An SR44 battery is a silver oxide battery (equivalent to #357) that is 11.6 x 5.4mm.

You can get these specs from any battery maker, like exellbattery.com. I don't have this exact MR-9 adapter, but I am certain that the difference between SR43 and SR44 is about whether the larger battery physically fits in your camera/meter when it's sitting in the adapter. If it fits, just try using the camera.

Thanks, That's what I think , without any current being drawn, the voltage remains unchanged.

 

[chuckroast]

Is the MR-9 adapter only accept SR43 battery according to the description from the packaging ? I don't have any SR43 to test, I had tried the LR44 and SR44w without the adapter the voltage shows 1.56v and 1.59v. With the adapter , the voltage did not drop to 1.35v as expected, it shows 1.51v and 1.52v respectively. I tried both adapters , the results are the same . These are the Kanto camera MR-9 from Japan. Also I tried the Zinc air 1.35 V with/without the adapter, the voltage remains 1.35 volt.
Any idea why ? thank you.

The MR9 solution will not drop voltage until it is under load. You're not loading the battery simply by measuring it with the device freestanding.

 

[runswithsizzers]

If a Schottky diode drops the voltage in relation to the current draw, then that brings up the question, How much current does a camera meter draw?

In other words, if one wants to check a MR-9 battery adapter to be used in a camera, what resistor value should be chosen to represent a realistic current draw?

In addition to a 20V DC setting, my multimeter has a Battery Test function for 1.5V, 9V, and 12V. Can I assume using the Battery Test mode of my multimeter adds some kind of load? The operating instructions do not say if a load is applied, or how much.

 

[chuckroast]

If a Schottky diode drops the voltage in relation to the current draw, then that brings up the question, How much current does a camera meter draw?

In other words, if one wants to check a MR-9 battery adapter to be used in a camera, what resistor value should be chosen to represent a realistic current draw?

In addition to a 20V DC setting, my multimeter has a Battery Test function for 1.5V, 9V, and 12V. Can I assume using the Battery Test mode of my multimeter adds some kind of load? The operating instructions do not if a load is applied, or how much.

It's designed for a nominal draw of 200 microamps:

MR-9 Adapter. Replacement for PX625, PX13 or MR9 discontinued Mercury cells.

 

[runswithsizzers]

It's designed for a nominal draw of 200 microamps

When it comes to electronics, I am a real babe-in-the-wood -- so, someone please help.

If I understand correctly (doubtful), and if I got the decimal in the right place for the amps, then is it true that a 7500 ohm resistor would be an appropriate load for testing the MR-9 voltage converter?

 

[wiltw]

The ones I have has a tiny diode at the bottom .

What I said earlier about so-called 'MR-9...they use the designation, they look similar, but they work differently -- NOT Voltage converting...

You have one like this...

[/URL]

...and the product description says, "The adapter fits for LR44 or a 1.4v Zinc air battery."
and since the hole is not needed for air to the cell, it probably simply lets air in so that expended cell will more easily drop out of the inset cavity because a vacuum does not form as the cell is withdrawn.

OTOH, this (different) product sold on the same website as an MR-9 is one with Voltage conversion, and costs more...
"US Duty Paid Kanto Camera MR-9 Mercury Battery Adapter SR43 1.55V to 1.35V New"

 

[reddesert]

If a Schottky diode drops the voltage in relation to the current draw, then that brings up the question, How much current does a camera meter draw?

In other words, if one wants to check a MR-9 battery adapter to be used in a camera, what resistor value should be chosen to represent a realistic current draw?

In addition to a 20V DC setting, my multimeter has a Battery Test function for 1.5V, 9V, and 12V. Can I assume using the Battery Test mode of my multimeter adds some kind of load? The operating instructions do not say if a load is applied, or how much.

Any type of diode will drop the voltage by some amount that ramps up from zero (it is a knee-like curve) depending on the current draw.

A normal silicon diode (like a 1N4001 rectifier) will drop the voltage by about ~0.7 volts at typical currents like a fraction of an amp. It would probably be about 0.5 volts at the tiny less-than-a-milliamp currents drawn by a light meter. That's too much, so the people who make MR-9 type adapters have to use a different type of diode. Something like a Schottky BAT42 diode would be a good choice. These use a metal-semiconductor junction and have a smaller voltage drop. Here's a datasheet for the BAT42: https://www.vishay.com/docs/85660/bat42.pdf

Figure 2 (see below) shows that at 25 C and a current of 0.2 milliamps, the BAT42 has a forward voltage drop of 0.2 V, which is just about exactly right.

The battery test mode of your multimeter might draw a few milliamps, I think that's what mine draws. This might be close enough to do the test. It would be more controlled to get a resistor and measure the device under a known load - it doesn't have to be exactly a 7.5Kohm resistor, it could be 5K, or 10K, and you'd still get a meaningful result.

But at some level, what are you planning to learn? These Schottky diodes are not exotic complicated parts; you can probably buy a BAT42 for 10 cents and it will last forever at camera voltages. The hard part is packaging the diode into the tiny space of the battery adapter, and that's what the user is paying for.

 

[mshchem]

What I said earlier about so-called 'MR-9...they use the designation, they look similar, but they work differently -- NOT Voltage converting...

You have one like this...

[/URL]

...and the product description says, "The adapter fits for LR44 or a 1.4v Zinc air battery."
and since the hole is not needed for air to the cell, it probably simply lets air in so that expended cell will more easily drop out of the inset cavity because a vacuum does not form as the cell is withdrawn.

OTOH, this (different) product sold on the same website as an MR-9 is one with Voltage conversion, and costs more...
"US Duty Paid Kanto Camera MR-9 Mercury Battery Adapter SR43 1.55V to 1.35V New"

Ebay deceiver

 

[koraks]

In addition to @reddeserts excellent explanation & illustration above: we need to realize that the current draw in a camera is not necessarily constant. Combined with the I/V characteristic of any diode, which is also not constant (see above), we can conclude that a diode-'adapter' will simply not result in a perfectly predictable & constant supply voltage to the camera. The question is whether that's a problem and I'd argue that in many cases, it isn't - otherwise the internet would have long ago exploded from horror stories about gross metering problems. Having said that, if you want to do it right, there are also adapters or guides to build them that use a tiny low-drop voltage regulator to create a truly constant (at least within more than reasonable bounds) supply voltage. See this thread (for instance) for more info: https://www.photrio.com/forum/threa...v-mercury-batteries-voltage-regulator.193257/