18-12-2015, 05:42 PM
It's been quite a good learning experience this book. It's more about trying to get an idea how the engineers had to work in that era when society was less industrialised. It seems money and cost was a significant factor and some engineers made their own all-purpose test meters using cigar boxes, sockets and home-made test prods.
Put simply, as I understand it, the way they had to think was like this: If you have a current meter that has a max of 10 milliamps and you want to test that a 1000 Ohm resistor really is 1000 Ohms, you have to start by multiplying the current by the resistance to get the voltage you'll be using. At that point they tended to grab a grid bias battery or an H.T. battery. The idea would be to make a circuit with the battery, meter and resistor to measure current. However, if the resistor happened to be very low due to a fault you didn't know at the time, and you applied the full battery voltage straight away, the current would go way over the limit and screw the meter. So, they simply tried first with, say, 1.5 volt and calculated what the expected current ought to be (if the resistance was 1000 Ohms). Obviously if you thought the resistor was O.K., applied full voltage but it was actually only 100 Ohms and not 1000 ohms, you could get problems as devices weren't fused.
So, basically, it's kind of fun to take a look at how people worked back then. No electric drills or digital testing gear. They even tested variable, moving vane condensers with a light bulb.
Put simply, as I understand it, the way they had to think was like this: If you have a current meter that has a max of 10 milliamps and you want to test that a 1000 Ohm resistor really is 1000 Ohms, you have to start by multiplying the current by the resistance to get the voltage you'll be using. At that point they tended to grab a grid bias battery or an H.T. battery. The idea would be to make a circuit with the battery, meter and resistor to measure current. However, if the resistor happened to be very low due to a fault you didn't know at the time, and you applied the full battery voltage straight away, the current would go way over the limit and screw the meter. So, they simply tried first with, say, 1.5 volt and calculated what the expected current ought to be (if the resistance was 1000 Ohms). Obviously if you thought the resistor was O.K., applied full voltage but it was actually only 100 Ohms and not 1000 ohms, you could get problems as devices weren't fused.
So, basically, it's kind of fun to take a look at how people worked back then. No electric drills or digital testing gear. They even tested variable, moving vane condensers with a light bulb.
