For every engineering and scientific activity, tools are key. At any expertise level, to do electronics, you must have a multimeter. That being said, you usually pick-up a model you can afford and has the right precision for your application. And today, we all have access to a broad range of devices that fit all budgets and projects’ needs. Because the price of the equipment is regularly dropping, while the quality & precision is improving, hobbyists rarely build their own multimeters these days. But that was often the case 45 years ago! The tool I am presenting today – the Heathkit IM-1202 Digital Multimeter – was available in 1972 as a kit than one could buy, assemble, calibrate and of course use. The IM-1202 can measure and display DC voltage and current, AC voltage and current – line frequency is the sampling rate –, and resistance (ohms); with a precision of 2.5 digits (and 10 mV, 10 uA and 1-ohm resolutions). The accuracy is DCV: +- 1%, DCA: +- 1.5%, ACV: +- 1.5%, ACA: +- 1.5%, and ohms +- 2%. Nothing sexy compared to what we can buy these days. To get a good feel of the age of this device, note that when you cold-switch-on the unit, to achieve the best accuracy, you have to give a 15-minute warm-up period. Woo, can you imagine doing that today? Now the really cool aspect of this multimeter: the display. It uses two nixie tubes for the digits, as well as four neon lamps to lit the one (1, this is the leading one, if needed), the plus (+), minus (-) and OVER symbols. A decimal point is also added when/where needed. One word on the polarity indicators (+ and -). You may have noticed a switch on the faceplate marked + and -. Well, you can use this switch to reverse the polarity, so you avoid swapping the measurement leads. A nice touch for the laziest among us! Overall, the Heathkit IM-1202 Digital Multimeter is a cute – not very accurate – multimeter, but a hell of a kit!
DC volts: 0-2, 20, 200, 1000 V
DC current: 0-2, 20, 200, 2000 mA (3 A max)
AC volts: 0-2, 20, 200, 700 V rms (25 Hz to 10 kHz)
AC current: 0-2, 20, 200, 2000 mA rms (25 Hz to 10 kHz) (3 A max)
Ohms: 0-200, 2K, 20K, 200K, 2000K ohms
If you love the glow of the nixies, you may be interest by this picture (and the related album): https://plus.google.com/u/0/photos/111136724877107811112/album/5978494043617555665/5978494258564192610
Heathkit did a lot of great electronics kits. In this post, I am presenting a computer kit!