Downloaded from https://www.everyspec.com MIL-STD-1311D METHOD 1311A ANODE RESISTANCE 1. Methods of determination. The anode resistance shall be determined graphically from the reciprocal of the slope of the graph of anode currents as ordinates against anode voltages as abscissas (other electrode voltages being maintained constant) or measured directly by means of the voltage-ratio method shown in figure 1311-1 or by an equivalent method. 2. Voltage-ratio method. The voltage-ratio method utilizes a system of transformers, capacitors, and attenuators to supply three independent, properly phased, and adjusted ac voltages (normally 1,000 Hz) from a common source.
The ac (rms) voltages E1, E2, and E3 shall be in phase and the output resistance of the attenuators made small by proper design in order to neglect the voltage drop due to electrode currents. The voltage ratio E2/E1 shall be accurately determinable. When a null is reached, ) ( 1 2 ohms R x E E rp = where R is a fixed resistor of 100,000 ohms. The anode resistance shall be within the limit(s) specified. FIGURE 1311-1. Simplified circuit for measuring anode resistance. METHOD 1311A 1311-1 25 March 1970