Downloaded from https://www.everyspec.com MIL-STD-1311D METHOD 1369 HEATER OR FILAMENT WARMUP TIME 1. Test circuit. The heater or filament warm-up time test shall be made in the circuit shown (see figure 1369-1). Before the test is made, the electrodes of the TUT shall be at or near room temperature. 2. Rs adjustment. The series resistor (Rs) shall be adjusted before the warm-up time as follows: Set open-circuit voltage at 4 times the rated heater voltage (Ef). Insert a resistance equal to Ef/If (bogey) in place of TUT. Adjust Rs such that voltage shown on a high-impedance voltmeter (E) is equal to rated (bogey) heater voltage (Ef).
Rs should not vary more than 5 percent during the following test. 3. Test procedure. With the switch open, insert the TUT into the socket. Adjust supply voltage to the proper value, close the switch and simultaneously start a timing device, accurate to 0.1 second. When the voltage reading of the voltmeter (E) reaches 0.8 Ef, stop the timer and record time. This time should be within the limit(s) specified on the TSS. FIGURE 1369-1. Test circuit for heater of filament warm-up time. METHOD 1369 1369-1 19 April 1968