Fluke 752A - Reference Divider

• 10:1 and 100:1 divider outputs
• Output uncertainty 0.2 ppm and 0.5 ppm
• Built-in calibration bridge
• Dynamic Resistor Matching™
• System switching for ease of use
• Operating modes

The Fluke 752A Reference Divider sets the standard for ratio accuracy and ease of use. It offers two divider outputs, 10:1 and 100:1 with output uncertainties of less than 0.2 ppm and 0.5 ppm respectively.

Before each use, the 752A is easily calibrated with only a stable source and a null detector. The entire procedure takes only five minutes and does not require external standards.

The calibration procedure compensates for long term changes in value of the divider resistors. The upper leg of the divider is configured into three equal groups, which, when placed in parallel, form a resistor of equal value to the output resistor. These two resistors form one half of a Wheatstone bridge. The other half is composed of two calibration resistors whose positions can be interchanged in the circuit. This interchange allows correction for any difference in the values of the calibration resistors through use of the BALANCE knob on the front panel. The upper leg resistors are then matched to the output resistor with the 10:1 or 100:1 potentiometers respectively.

Operating modes

In the stand-alone divider mode, input to the divider is applied to the INPUT terminals and is switched by the MODE switch to either the 10:1 or the 100:1 position. Output from the divider is then available at the OUTPUT terminals.

When the 752A is augmented with a 10V reference source and a null detector (such as the Fluke 732A and 845AB), the resulting system becomes a 5-decade cardinal point voltage calibrator with facilities for comparing input voltages of 1000V, 100V, 10V, 1V and 0.1V to the 10V reference. In this mode, the voltage source to be calibrated is connected to the 752A input terminals and the MODE switch reconfigures the system for each of the ranges with no manual lead changing necessary.

When the MODE switch is turned to the 752 CAL position, the 752A divider resistors are switched to form a bridge circuit with the two additional calibration resistors. Bridge excitation is supplied from the voltage source (set for an output of 20V) connected to the input terminals and the null detector is switched across the bridge to measure bridge balance.

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752A Reference Divider

Division Ratio Division Ratio 10:1 ±0.2 ppm Input: 0V to 100V Division Ratio 100:1 ±0.5 ppm Input: 0V to 1000V General Specifications * Ratio Ranges   10:1 and 100:1 Ratio Uncertainty   Ratio accuracies that apply for a temperature variation of less than ± 1°C from the self-calibration temperature (between 18°C and 28°C) for up to 8 hours following self-calibration:   -------- Range 10:0 Input Voltage: 0 to 100V   Output Uncertainty: 0.2 ppm   Null Accuracy: ±0.5 mV**   -------- Range 100:1 Input Voltage: 0 to 1000V   Output Uncertainty: 0.5 ppm   Null Accuracy: ±1.0 mV** Temperature Coefficient   £ ± 1 ppm per °C over range of 18°C to 28°C (typically 0.1 ppm per °C from 15°C to 30°C Input Resistance 10:1 Ratio: 380 kΩ ± 1% 100:1 Ratio: Divider is 4 MΩ; Driven Guard is 4 MΩ; total is 2 MΩ ± 1% Maximum Input Voltage   200V for the 10:1 ratio   1100V for the 100:1 ratio Power Coefficient   £ 0.05 ppm of output with 100V applied for 10:1 ratio and £ 0.3 ppm of output with 1000V applied for 100:1 ratio (included in the ratio accuracy specifications) Temperature   0°C to 50°C, operating; -40°C to 75°C non-operating Relative Humidity   £ 75% to 40°C, £ 45% to 50°C, non-condensing, operating; £ 100% 10-50°C, non-operating Altitude   £ 3050m (10,000 ft) operating; £ 12,220m (40,000 ft) non-operating Vibration   Per MIL-T-28800C, Type III, Class 5, Style E Safety   IEC 348, 2nd edition, 1978; ANSI-C39.5, 1980, CSA 556B, and UL 1244 Size   19.1 cm H x 22.1 cm W x 60.3 cm L (7.53 in H x 8.69 in W x 23.75 in L) Weight   8.4 kg (18.5 lbs.) *Specifications apply for the lifetime of the instrument over the temperature range of 18°C to 28°C. **Null accuracy refers to the required accuracy of the null detector reading during self-calibration.