| 摘要 |
The invention relates to an electromagnetically force-compensating force-measuring apparatus (100) comprising - a support coil (2) which is mounted in a permanent magnet arrangement and through which a coil current (IS) produced on the basis of the force using a controller (4) flows during operation, and - an integrating analogue/digital converter (10; 10') which is set up to convert an electrical signal (UM), which is representative of the coil current (IS) and is applied to the measurement signal input (14) thereof, into a digital output signal, wherein the analogue/digital converter (10; 10') is connected, at the reference voltage input (18, 20) thereof, to a reference voltage source which has two reference voltages (URef1, URef2), which are of the same magnitude and are oppositely polarized with respect to one another, and alternately connects a reference voltage switch (16) to an integrator (12) of the analogue/digital converter (10; 10'), wherein a ratio of the intervals in which the individual reference voltages (URef1, URef2) are connected to the integrator (16) within a measurement cycle is a measure of the currently flowing coil current (IS). The invention is distinguished by the fact that the output of the controller (4) is connected, via a first heating resistor (RSH), to the output of a voltage amplifier (8), the input of which is connected to the output of the reference voltage switch (16), and by the fact that a current/voltage converter (6) is connected downstream of the support coil (2), the output of said converter being connected to the measurement voltage input (14) of the analogue/digital converter (10; 10') and, via an inverter (9) and a second heating resistor (RWH), to the input of the voltage amplifier (8), wherein the resistance value of the first heating resistor (RSH) is equal to the resistance value of the support coil (2), the resistance value of the second heating resistor (RWH) is equal to the conversion factor (RW) of the current/voltage converter (6), and the gain factor of the voltage amplifier (8) is equal to the quotient of the resistance value of the first heating resistor and the resistance value of the second heating resistor. |
