A very important circuit in the 1960s was the voltmeter, which, taking advantage of the high impedance characteristics of this device, enabled accurate measurements with common analog instruments.
The circuit shown uses a 6SJ7 valve with 250 V supply and as an indicator instrument a milliammeter of 1 mA full scale.
The scale is determined by the settings thus allowing the measurement of voltages with an input impedance of several megohms.
In the circuit does not appear the power supply that also must have resources to feed the filament of the valve. See in the article Sources for Valve Actuators how to power this circuit.
In figure 1 we have the diagram of the voltmeter.
Figure 1 - Diagram of the voltmeter to the valve. | Haga click en la imagen para ampliar |
