MR meter with 1.5 volt battery

<p>When I bought an MR meter from a Leica maven a few years ago, he said the meter would work with a 1.5 volt battery. I had a couple of mercury batteries--the requisiter 1.35 volts--so I used those instead. Now those are dead and I have finally put in a 1.5 that's the same size as the old mercuty 1.35s. The meter seems to be on the dot anyway, even by the sunny 16 rule. Anyone else have this experience? Does the MR have a circuit that's not bothered by the voltage difference? </p>

<p>Some newer metering systems will work with a alkaline cell.<br>

the discharge charatristic of an alkaline cell is sloping. beaning gradually fades away.<br>

the mercury cell 1.35v stays close to that voltage and after perhaps 2 years just dies.,<br>

the silver oxide cell is 1.55v and acts the same way. so it will give wrong readings.<br>

the zinc air cell has a short life between 3 months and a year ( roughly)<br>

it starts at 1.4v and at the end dies. Commonly know as hearing aid cells sold in the pharmnacy.<br>

it is the closest thing you can get and works well..<br>

the wein cells are similar but sold in camera stors.<br>

the chris adapter uses a silver cell and a shottky diode.<br>

it is a expensivbe vbut good replacement for the mercury cell.</p>

<p>Many older metering curcuits used a series arrangement that was very dependent on the cell voltage.<br>

this applies to most devices that used mercury cells.<br>

a few like Pentax used a bridge or malancing circuit that was fairly tolerant of an unstable voltage as provided by an alkaline cell.<br>

I tryed to tell this to the NIkONIANS. but it sailed right over his head.<br>

with B&W and Color print film you can get away with some of this and never realize it.<br>

Sort of turning you Leica into a cheap P&S with a sharp lens.</p>

<p>If you are using it casually use the hearing aid cells.<br>

if you will use it a lot get the CHRIS adapter or see if the meded can be modified to use a siivber oxide call.<br>

if you do see if a small label can be added to say this.</p>

<p>I do not think the MR meter has a "bridge" circuit to regulate voltage. Please understand Walter's explanation of the difference between alkaline cells, whose output voltage is not steady, and silver oxide cells. An adapter with a diode was made also by the Dutch engineer Frans de Gruijter. They cost a good deal less than the CRIS product, and the three I had worked faultlessly. See http://www.buhla.de/Foto/eQuecksilber.html</p>

<p>Generally, if the correct exposure is shown when the meter's needle is in the centre of its travel and this is also the needle's resting place when the meter is off, it has a bridge circuit. Correct exposure is when the current through two parallel circuits is equal and no current flows through a meter connected between the middle points of both circuits. This is a bridge circuit and any cell which you can make fit and make contact will work without any worry about voltage or discharge rate.</p>

<p>If the correct exposure is worked out either by matching a second needle to the meter's needle or transferring the number it points at to a table. i.e. correct exposure could be represented by any position of the needle, then it is not a bridge circuit and it is highly likely that the circuit is voltage dependent. </p>

<p>Oh man, here we go again on the batteries...use a PX-625 alkaline and go enjoy shooting and using the meter. suffice to say a noted repairperson recommends them. They work just fine. </p>

<p>It will work fine. The problem is that modern alkaline batteries will not give you any warning when they lose juice, your metering will just become worse and worse, slowly. So you would want a silver battery or the Wein cell batteries, (or the much cheaper hearing aid batteries w/ a shim to take up the lesser diameter issue). Just replace them every 2 months or so and that will do it. Here's a link to someone that knows a lot more about it than I do. It's spelled out very nicely.</p>

<p>http://rick_oleson.tripod.com/index-111.html</p>

<p>I think that the voltage adapters with Zenner diode circuits are not a good solution, because the voltage varies greatly depending of the lightmeter circuit resistance of the camera and by this, the intensity.</p>

<p>A few years ago I found a Weston Master IV and had a new selenium cell installed by Quality Light Metric in Holywood. It's accurate and completely eliminates the battery problem. I realize it's a bit off-topic, but may be of interest to some.</p>

<p>I have found that the MR meter with the CRIS adapter has produced perfect results for many years.</p>

<p>Also that Quality Light Metric's repair of Weston Meters is excellent. If you can find a non-working<br>

Weston Master III or IV at a camera show for next to nothing, send it to QLM for a cell replacement.</p>

<p>In math classes I took many years ago 1.35 rounds off as 1.4 so are zinc/air cells really 1.35 volts? (I've used them in place of the mercury cells with an Oring around them and they always work fine.)</p>

I bought the same adapters as Mukul for my Canon F1s and they work perfectly and have done for many years. They

allow you to use silver oxide cells but meter correctly (the other option is to have the meter re-calibrated to the higher

voltage).

<blockquote>

<p>"a PX-625 alkaline" - "suffice to say a noted repairperson recommends them" <em><strong>Will W.</strong></em></p>

</blockquote>

<p>Higher incidence of corrosive leakage for both, and lack of stability of declining voltage from the alkaline units, I'd avoid the Zinc-Air and Alkaline batteries.</p>

<p>Whenever possible & whatever your combo (Re-calibration, washers, spacers or adapters), utilize the <strong>Silver Oxide</strong> offerings.</p>

<p>I solved the entire problem yesterday, completely and finally. I lost the MR in a taxi; I'll never see it again. I was really upset when I realized what had happened, but I went straight to a camera store and got the Voigtlander VC II meter. I only hope that whoever finds the MR will give it to someone who can use it and not throw it away. </p>