Section 4
OM7520-B-00
27 September, 2019
4-1
4.
THEORY OF OPERATION
4.1.
INTRODUCTION
The Guildline Model 7520 Precision Voltage Divider is designed with an extremely stable
voltage divider resistor chain with three divider sections (i.e. each with separate resistors
that provide a 1:10 ratio) with low thermal offsets. The Voltage Divider is contained in a
temperature controlled and EMI shielded chamber. Input voltages can be anywhere within
the range of 0.01 to 1100 volts. Any voltages between 10 and 1100 Volts can be divided by
ratio of 1:1000, 1:100, 1:10, 1:1, 10:1 and 100:1 with uncertainties (uncertainties are used
rather than accuracies as in the table in section 1.4) of 0.5, 0.2, 0.1, 0.05, 0.1 and 0.2 µV/V
respectively to be compared to a 10V voltage reference when using the Comparator mode.
The voltage divider is fully controlled by an internal micro-processor through a front panel
touch screen.
Several systems are used to protect the devices connected to the divider and the voltage
divider itself from being damaged by operator error or internal failure. The 7520 Voltage
Divider can be operated from the front panel touch screen or by commands sent over the
USB or GPIB Interface.
4.2.
LOW THERMAL DESIGN
Special care has been taken to minimize thermal offsets. Very stable resistors are used
with a low temperature coefficients and minimal self-heating. The switches used are low
thermal relays.
The main voltage divider chain and associated relays are housed in a temperature
controlled enclosure. This isothermal enclosure helps to maintain a uniform temperature
throughout the divider chain so as to minimize thermal offsets and maximize stability of
the resistance divider components. The stability of the temperature controlled chamber can
be monitored from the touch screen display.
