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Introduction


The Simpson 260 Series 8P is an analog volt-ohm-milliammeter with relay-based overload protection.

It is a newly-made meter from Simpson Electric, upholding the tradition of the great Simpson 260 series.

So let's see what it's all about.


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In This Article


Decibel Scale

Front Panel & Range Switch

Input Impedance / Resistance

Millivolts AC

Millivolts DC

Ohms Measurement

Packaging Issue

Relay Protection

Voltage Measurements

Special Abilities

Why a 260?

New Or Vintage?


Conclusion



Decibel Scale


-20 to +10 dB.  Obviously this is electrical Decibels, not sound. 

Because the scale is non-linear, you get the best readability / resolution between -2 and 10 dB.



Front Panel & Range Switch




For the most part, it's the classic Simpson 260 layout with all the usual range selections.  There is one major difference you might overlook, something that many of the earlier series lacked.  That's the 25-volt range.  Excellent for testing car batteries, because it has finer resolution than the 50V range.

Outside of this, there are a couple additions and improvements.  The voltage type selector (AC, +DC, -DC) adds a fourth selection:  Continuity tester.  Next to the Simpson logo, you'll also see the white button for the Relay Protection reset. 

The range switch has the usual setting for 250V, with "500V" and "1000V" in the same place.  This depends on which voltage jack you have the red test lead plugged into.  It's a slight change from some of the older Simpsons, which had only 250V and 1000V.

As with many of the earlier 260's, the 50V position says "50 uAMPS" (50 microamps, and that should be "mu" not "u", but I was too lazy to type the correct HTML code for it).  Again, depends on which jack you have the red test lead plugged into.

The knobs and switches are the usual high-quality phenolic type, as it should be.


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Input Impedance / Internal Resistance


20,000 Ohms per Volt DC

5,000 Ohms per Volt AC


This will cause some circuit loading, basically a voltage drop because you're putting a resistor (namely, the multimeter) across the voltage being tested.  (Any voltmeter is like putting another resistor in parallel with a circuit.)  As the old-timers knew, many radio and TV repair manuals show test voltages that take this fact into account.  So with those, if you read the voltages with a digital meter-- which has a much higher input impedance-- you'll get the wrong voltage. 

Outside of that, you could conceivably get the wrong measurement with a low-impedance meter like this.  But the question is, how much of an issue is it?  For all-around use, it's not that big a deal.  There are some situations where a reading might be off by 10% or something, but it's useful to know that there's a "ballpark" correct voltage there instead of no voltage at all.  This is why the Simpson 260 is still my go-to piece of test equipment for almost anything.

This is not a FET meter, so if you do need high input impedance / resistance, get one of these instead (20 Megohm internal resistance).  But the 260 is a brilliant piece of equipment, and after you use it for a while you'll get a feel for how much it affects the reading.  Besides, on higher ranges the circuit loading becomes much lower.  On the 25V range it's 500 kilohms, and on the 50V range it's 1 Megohm.


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Millivolts AC


Sort of.  Resolves down to about 100 millivolts AC, maybe 50.  Useful for testing stereo speaker wire connections, where the typical AC voltage is from there to about 2.5 volts.  Here, the Simpson acts almost like a VU meter, which is something you can't see with a digital multimeter.  (I know:  digital bar graph indicators, but they're just not the same.)





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Millivolts DC


Yes.  0 to 250 millivolt scale.  Resolves down to about 5 millivolts (0.005 volt) DC.

So, while it's not going to compete with the higher-resolution DMM's, you can use this meter for some fairly low-voltage electronics.


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Mirrored Scale


Yes, and it's the real deal, not one of those hazy brushed-aluminum sorts that you'll find on cheaper meters.


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Ohms Measurements


The ranges are Rx1, Rx100, and Rx10,000. 

It would have been nice to see an Rx1000 range on here, but this is normal for the Simpson 260 series. 

On Rx100, you can measure resistors up to 10K ohms.  However, because the scale is non-linear, precision and readability fall off between 3,000 and 10K ohms.  It really falls off quickly in the upper portion of that range.

On Rx10,000, you can measure up to 1 megohm.  Here again, precision and readability diminish between 300K ohms and 1 megohm. 

This is typical for analog VOM's.  The Ohms scale is non-linear, which means you get lower-precision readings farther out on the scale.  So, if you have to read a 9K ohm resistor or a 470K ohm resistor very precisely, you'll want to use a digital meter for that.  Maybe.  Here's a story for ya.

One day I had to measure something that was 0.9 Megohm.  The Simpson nailed it;  in fact, it worked in a situation where a Hewlett-Packard DMM was flaking out due to EMI and kept saying 0.5 Megohm, 0.3 Megohm, etc.  The Simpson 260 was better than that sophisticated digital meter;  who'd have thought? 

Now, the resolution and accuracy might be no better than 5% at those ranges, but if you zeroed it properly and you're good at reading these things, maybe it's better than that.


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Packaging Issue


The one drawback is the packaging.  They used a regular plastic bag, when they should have used a metalized one.  The 260-8P does contain transistors (one, at least) and diodes.  A proper metalized bag would cost less than 99 cents and would create a lot more confidence that you're getting a multimeter that will last for generations. 

It probably still will last for generations, but there's always that wondering, "What if it degraded the semiconductors just a little bit?"

Semiconductors don't always fail "digitally".  There are varying degrees.  If the transistor degrades, the relay protection could fail to activate properly. 

This is such a great meter, and I still think it's worth getting, but they need to improve the inner packaging. 



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Relay Protection


In addition to the standard input protection you'll find in all newer Simpson 260's (diodes, fuse), the 260-8P also has relay protection.  Batteries have to be installed for the relay to work;  make sure they're fresh before using the meter.

There's a transistor circuit that senses voltage, and if it's about 3x the scale rating, a relay opens the circuit instantly.  It's a resettable switch:  that white button on the front of the meter. 

Simpson 260's are great meters, but the relay protection makes them even better.  It doesn't even cost that much more than the regular Series 8.  I would get the relay one. 


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Voltage Measurements


Voltage scales shown around the dial are 2.5 volts, 10 volts / 1 volt, 25 volts, 50 volts, and 250/500/1000 volts. 

The 500 and 1,000 volt ranges require the use of dedicated test-lead jacks.  There's also a 0 to 1-volt range, which again has its own jack.

There's also a 0 to 250 millivolt scale.  For this, use the "+10A / +50uA / 250 mV" jack.

Unlike the Ohms scale, the voltage scales are linear.  Readability is good throughout the ranges.

The 25-volt scale is a welcome addition;  this allows the measurement of car battery voltages with greater precision.  It's that 12.6-12.8 volt range you really want to be able to distinguish from your basic "12 volts".  And this meter is going to be way more accurate than cheap DMM's, some of which can't even seem to do 5 or 6% accuracy (despite impressive specs on paper.)

The 2.5 and 10-volt ranges have low input impedance (actually, DC resistance).  Measuring a source with high output resistance (such as a very small battery) could drop the voltage significantly.  Then again, think of the meter on the 2.5-volt scale as a 50k Ohm resistor.  It doesn't drop the voltage that much across a AA battery.  I read 1.45 volts on a AA battery, probably well-used, that was sitting on my desk.

After you use this meter for a while, you will learn how the voltages read.  So you'll be able to know when batteries are still good, even though the readings may not make as much sense to a beginner.

(By the way, this meter gives accurate readings of a car battery, because a car battery is a "low impedance source".)

On the 50-volt scale, now the input resistance is 1 Megohm.  And on the 250 volt scale, it's 5 Megohms. 

And as I said, once you learn the way it behaves on the lower ranges, you'll know what readings to expect.



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Special Abilities


A huge reason for getting an AMM, especially a good one like this, is the precision analog meter movement.  This allows you to spot voltage fluctuations that would make no sense on a digital multimeter.  I hate watching the numbers jump around on a DMM meaninglessly.  It always makes me feel like there's something wrong with the digital meter, like maybe I zapped it somewhere along the lines.  Or maybe it's flaking out because of EMI/RFI.  The 260 won't do that.

Analog meters are the ideal choice when you have to measure changing voltages. 

There are many uses.  A few examples:

- Detecting changes and trends in voltage
- Finding defects in variable resistors.
- Watching a capacitor-discharge curve.  (Pick a voltage scale high enough for it.)
- Operating where there's a lot of RF that would make a digital meter go haywire. 
- Watching the voltage drop when you close a switch, turn on a DC lamp, etc.
- Testing a car battery when starting the car (Needle shouldn't drop below 10 volts)
- Troubleshooting intermittent connections, relays, solenoids, and other stuff where you want a quick visual indication

There's even a way to measure AC frequency with a Simpson 260, up into the hundreds of Megahertz, if you rig up a HF diode and a couple other things. 


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Why a 260?


It is refreshing to use things that are actually well-built. 

There are classic designs that simply do not need to change. 

The Simpson 260 does what we want it to do.  It has that solid, well-made design that hearkens back to the late 1930's and 1940's.  The manufacturer is one of those rare companies that has the sense to keep making a classic design.  Win!!


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New or Vintage?


There are vintage Simpson multimeters out there, but the used ones can have a variety of issues.  Battery corrosion and drifted or open resistors are very common.  Many issues are fixable, but how long does that take?  Vintage test gear has a lot of unknowns.  It's always possible you could get one with a bad meter movement.

Get a new one, and you won't have to deal with anyone else's issues, hack repairs, etc.  Brand-new, calibrated from the factory, and ready for a lifetime of use. 

And actually, when you adjust for inflation, these meters really aren't any more expensive now than they were.  Totally worth it.  I didn't even think I would say that, but once you get one of these meters in your hands, wow. 


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Conclusion


Simpson Electric makes one of the best analog multimeters in the world.  Actually now that the Triplett 3030 is not made in USA anymore, Simpson 260 is the king.  This is a professional-quality tool that was designed for a lifetime of use.  Take good care of it, and you'll have one of the all-time best, classic pieces of test equipment.

The only real dislike is the packaging materials they used.  They really need to start using a metalized anti-ESD bag for the inner packaging.  For now, I would unpack this in a high-humidity environment to minimize the static voltage buildup.  Even though there's not much to go wrong with an analog meter, there are diodes and at least one transistor in this one.


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