Tale of Two Meters

Today was a good day as two meters were added to my family of meters. I would not usually write about the addition of a meter or two but the contrast between these two meters is special. Many of you have experienced and appreciate the miraculous development of technology over our relatively short lifetimes. It takes a certain level of understanding and immersion in a technology to really appreciate the change and to truly experience the wonder of the change.

60 years ago I was just beginning my path into the adventure of electronics. While a rudimentary transistor actually existed before I was born they had not come into the main stream and my first contact with electronics was with tube (valve) technology. The glow of the heater filaments, the smell of hot resistors and components was common as well as a potential jolt at every connection. I want to set the stage by giving you this introduction as this was the world that one of my new meters was born into. In August of 1958, 60 years ago, the Anton Electric Lab TS-505D/U Vacuum Tube Voltmeter was one of the top multimeter type test instruments available. It was manufactured primarily for the US military and as such it was built for precision and utility under extreme conditions. I do not know how much they cost in those 1958 dollars but I am confident that it was high enough to seem unreasonable.

When I walked into the Retro Electronics shop yesterday the shop keeper, a kindly woman who had inherited the business a few years ago from her husband, was busy trying to clean some old equipment. She explained that someone had dropped off a bunch of equipment that had been sitting in their garage for years. I recognized the different pieces of equipment like an old Heath Kit Oscilloscope, a transistor tester about the size of a cigar box, a dot bar generator, a continuity tester, and off to one side covered in a coating of dirt that looked like it had been painted on was a metal box about the size of a 6 pack of beer. Equipment like this makes me nostalgic and I have to be careful or I end up going home to add more depth to the hoard of equipment that I already have but don't use.

I asked Judy what the box was and how much she wanted for it. She was a little overwhelmed with all the junk equipment and I could tell she just wanted to be free of it. Her husband was the electronics guy before he passed and while she had helped in the business her knowledge and interest in electronics has never grown past knowing where to find what people ask her for. She did not know what it was so I popped the box open by releasing the 4 cantilevered latches on the cover. I told her it was an old quality meter. She gave me a price and I took it. She also tried to get me to take the rest of the stuff too but, counting me, there is already one too many outdated relics in the shop and with this new acquisition we will have to make room for one more.

Here is a picture of the two new meters. The little one came all sparkly and new and the other one has had a multi-hour cleaning before it was ready for this picture. I will continue talking about the Anton Multimeter and get back to the little modern meter a little later in the blog.

Bless the internet I was able to download and print a full US Army Manual as well as a full set of schematics for the Anton Multimeter. Besides being encased in metal there are rubber o-ring seals between the meter and the back housing and the meter and the front cover. The test leads are even sealed water tight where they come through the face of the meter. I am sure that when it was new it could be dropped in a lake and retrieved a day later in perfect working order.

The function knob feels of quality when it is turned. Remember the first time you got into a quality car and pulled the door shut, I got the same feeling turning that knob that I got when at age 16 I was asked to go and pickup the boss of the auto parts store where I worked, in a neighboring town, using his new 1965 Chrysler New Yorker.  Zoom! What the function knob doesn't do however is switch the test leads. There is a separate test lead for DC Volts, AC Volts, and Ohms, as well as a Common Lead.

Here is a close up of the front control panel:

Last night I had a wonderful time as I took it apart and inspected it as I cleaned it. The outer case was so dirty the only fix was to remove it and scrub it in the sink with 409, soft scrub, and hot water. Here is what the meter looks like on the inside:

According to the army manual there are no electrolytics used in the unit. The tubes are all designed to be used at sub specification heater currents so they last longer. In the day, all parts were standard and easily replaceable in emergencies. If you look closely you can see a single fuse type clip on either side of the transformer. These clips hold spare germanium diodes. I cleaned the face of the unit of dirt but fortunately the seals had been good, the rubber was still soft, and the internal electronics were as clean as the day they were assembled. I plugged the unit in and turned it on. The glow of the #47 pilot light and the faint glow from the *** on the top of the tubes was reassuring.

My first test was a DC voltage test of a set of 4 AA batteries in a pack. I had my Fluke hooked to the pack too so I could see how well the two compared. These old meters are not as plug and go as the new ones. It is necessary to touch the probes together and set the zero before a measurement is taken. From turn on you can start taking measurement in a minute but the manual recommends 3 to 5 minutes is better. (The tubes have to warm up) After setting the Zero and touching the probes to the battery contacts the meter settled as close to what the Fluke was reading as my eyes could determine. I do not know how many years this meter has set since it was last turned on but the accuracy of the first measurement was excellent. Tests of the Ohms scales gave similar accurate readings. Of course it was necessary to set the zero and the Ohms calibration knobs before testing but that is just the way it was. When I say it was accurate of course I mean it was accurate to 2 digits and a guess while the Fluke was busy flashing its 4th digit. The only disappointment was that the AC was reading about 10% low. I hoped that I could correct this with calibration which I did a little later. However I was not able to fully correct the low reading. Apparently there is some cost for 60 years of existence. After studying the schematic I had some ideas on how to fix it but the fact is this meter will never be used where it is critical and I did not feel like taking a chance with old wires and old parts and making things worse.

The wires on the AC probe and Common were replaced but the old probes themselves were reused for as much authenticity as possible.

The other meter that came in the mail the same day that I brought the Anton Multimeter home was a $13.00 True RMS Mustool MT 66 4 digit Multimeter.

The cost of only $13.00 which includes a free ride from China doesn't leave a person to expect much. As usual I always put a new meter through its paces and take comparison readings against my more expensive meters. The little Mustool Meter held its own. Surprisingly it is auto ranging and has all the protections. After all my tests I was smiling and knew I had a great little meter to take with me whenever I have something to measure outside the shop. So how does one of the most expensive multimeters from 1958 stack up against a 2018 cheapy.

                                        Anton TS-505D/u                                        Mustool MT66

Cost                                  ? $500.00                                                           $13.00

DC Volts                              1000V                                                               600V

AC Volts                              1000V                                                               600V

Ohms                                   0 to 1 giga Ohm                                               0 to 60 mega Ohm

Resolution                            2 to 3 digits maybe                                          4 digits

Accuracy                              5 - 6%                                                              1 - 2%

Power                                   120 Volts  100 Watts Approx                           2 AAA Batteries

Weight                                   18 Pounds                                                       9 Ounces

Capacitance Test                    None                                                              1 pF to 100,000 uF

Diode Test                              Use Ohms Scale                                             Diode Forward Voltage resolution 1 mV

Sound Continuity                    None                                                              <30 Ohms Sounds

Frequency                              None                                                             0 to 100 mHz

Duty Cycle                              None                                                             10 - 95%

DC Current                         Use Volt Scale and Shunt                                   .1 uA to 10 Amps

AC Current                         Use Volt Scale and Shunt                                   .1 uA to 10 Amps

Temperature                           None                                                               - 30 C to +400 C

EMF Alert                              None                                                                 Yes

Now you get a good picture of just how far we have come in only 60 years. The TS-505D/U looses the battle to the Mustool MT66 today. However if we have another rematch between the two in let's say 2078 I will put my money on the TS-505D/U to still power up and do what it was designed to do while the plastic case of the Mustool will undoubtedly be floating in the ocean somewhere between here and New Zealand.

John