Abstract: A precision-delivery and precision-pressure piston pump is actuated by a cam controlled by a finestep stepping motor. The initial delivery pressure is precisely regulated by fixing the commencement of the delivery stroke at the cam with the aid of the stepping motor, as well as the time required for this delivery. Delivery is also regulated very precisely, for example in a ratio of 1 to 1000 by controlling the delivery stroke with the aid of the stepping motor. The pump is of use in particular in high-pressure liquid-phase chromatography.

Abstract: In a stepping motor (M), the windings (L1 to L4) can be switched with the aid of switches (111 to 114). Two windings of each pair (e.g. L1 and L2) cannot be brought into the circuit simultaneously and are together arranged in series with a resistor (146) and a transistor circuit (150) adapted to cut off the supply voltage of 25 volts. A comparison and control circuit (130) compares the winding current from the resistor (146) with a reference value which is determined by a digital balancing resistor network (120) controlled by a permanent memory (102) and consequently acts on the form factor of the interruptions of the 25 volt supply current by the transistor circuit (150). The invention enables the multiplication of the number of steps per revolution which can be carried out by a stepping motor.

Abstract: The automatic electric battery charging apparatus includes at least one timer, a voltage comparator arranged to compare a reference voltage, referred to herein as a staircase voltage, with a control signal varying with battery voltage, jacking means rendered operative by the timer when a first predetermined time interval has elapsed and serving to repeatedly increase the staircase voltage step-by-step relatively to the control signal, by equal steps, so long as the control signal exceeds the reference voltage, and terminating means for initiating the termination if the staircase voltage exceeds the control signal before the jacking means have exceeded a predetermined number of steps from the start of their operation.

Abstract: A battery charger which provides a constant current charge during a first part of the charging period and a taper charge during the remainder of the charging period. The taper charge characteristic is obtained by decreasing a set value for the charging current by a step of predetermined size each time the battery voltage has risen by a step of predetermined size, provided that the battery voltage is above a certain threshold; below this threshold, the set value has its maximum value, resulting in the constant current part of the charge. The charging current is regulated to be equal to the set value, regardless of variations in mains supply voltage. The charge is terminated when the time between steps in battery voltage exceeds a predetermined value.

Abstract: A controller for incorporation in a battery charger to limit the overall length of the charge, and also to provide short topping-up charges at intervals after the main charge has been completed, if the battery is left connected to the charger. The controller allows the limit on the length of the charge to be set to either 10 or 141/2 hours; the subsequent topping-up charges then start at intervals for 10 or 141/2 hours, and last for about 40 or about 55 minutes, depending on the setting of the main charge time limit. The controller is illustrated in conjunction with a charger control circuit which terminates the main charge when the rate of rise of battery voltage falls below a predetermined value, and this is normally expected to occur before 10 (or 141/2) hours have elapsed, leaving the time limit set by the controller as a safeguard.