Can a 9V battery for multimeters and process calibrators be replaced by a 1.5V battery boosted to 9V?
Multimeter and process calibrator of these instruments are generally not large, like the general operating current of the digital multimeter is mostly in the 20mA below, so it can be used 1.5V dry cell (or 1.2V nickel-metal hydride batteries) through the boost circuit to replace the 9V stacked battery. The following is a simple and easy to make 1.5V to 9V voltage regulator circuit, which can replace the multimeter with 9V stacked battery.
Circuit, transistor 9013 and 8550 form a complementary self-excited multi-harmonic oscillator, the two tubes work in the switching state. t for the step-up transformer, the primary coil as the 8550 transistor collector load, 8550 collector output of oscillating signals by the transformer T step-up, the secondary stage of the high-frequency alternating current voltage generated by the voltage by the Schottky diode 1N5819 rectifier, C2 The voltage is rectified by Schottky diode 1N5819, C2 filter and voltage regulator VD2 regulator, the output is a stable 9V voltage at the Vout terminal.
The oscillation frequency of the circuit is mainly determined by R2 and C1. General oscillation frequency can be selected from 5 to 20 KHz. the output voltage of the boost circuit is determined by the voltage regulator VD2 regulator value. If you need a stable voltage of 9V, you can choose 1N4739 regulator, the regulator value of 9.1V, the power of 1W. due to the secondary output of the transformer is a high-frequency alternating current voltage, so the VD1 should be selected with high-frequency performance of the switching diode or Schottky diode. Capacitor C2 is best used for high-frequency filtering good tantalum capacitors. the size of R3 depending on the voltage at the ends of C2 and the actual operating current of the multimeter. Here it is assumed that the voltage at the ends of C2 is 15V, the current flowing through the VD2 is 10mA, the maximum operating current of the multimeter is 15mA, then R3 can be taken as a 240Ω resistor.
The circuit of the step-up transformer can be selected from ferrite toroids around the system, the number of turns of the primary coil and secondary coil and wire diameter shown in Figure 1. Ferrite magnet ring can be removed from some of the scrap electronic ballast or switching power supply.
When making it, the β of the two transistors is as large as possible. The power switch S in the circuit can use the power switch of the original multimeter. The circuit can be powered by a #5 dry cell battery or a 1.2V NiMH battery.
