Biddle AVO 72-432 Electrical Test Instrument

The Biddle/AVO 72-432 is a precision instrument designed for accurate electrical testing, primarily functioning as a portable Wheatstone bridge. This device is engineered for the precise measurement of resistance values, employing the Kelvin Bridge method to eliminate errors associated with lead and contact resistance, particularly when measuring low resistance values. The instrument is self-contained, featuring integral batteries and a null detector for standalone operation.

### Technical Specifications

* **Type:** Portable Wheatstone Bridge (Kelvin Bridge configuration)
* **Resistance Measurement Range:**
* Catalog No. 72-439 (related model with similar functionality): 0.01 microhm to 1111.1 ohms in 7 ranges.
* The 72-432 is identified as a portable Wheatstone bridge, and sister models like the 72-430 also utilize this technology.
* **Limit of Error:**
* Catalog No. 72-439: (0.03% of reading + 0.03 microhm).
* **Measuring Circuit:**
* Kelvin Bridge form for four-terminal resistance measurements.
* Consists of two fixed arms and two mechanically-linked adjustable arms forming the ratio arms.
* Features a measuring dial with 5 decades for resistance steps.
* Resistance steps equivalent to 10 (0.1 + 0.01 + 0.001 + 0.0001 + 0.00001) ohms.
* Total range of 1.1111 ohms in steps of 0.00001 ohm.
* **Multiplier Dial:**
* Nine-position rotary switch for selecting multipliers and functions.
* Provides equivalent multiplier values of .001, .01, .1, 1, 10, 100, and 1000.
* Automatically selects the proper current limiting resistor to prevent damage to the bridge.
* **Null Detector:** Solid-state null detector integrated within the instrument.
* **Power Source:**
* Integral batteries for self-contained operation.
* Measuring circuit typically uses two 1.5-volt No. 6 dry cells (NEDA 906) connected in parallel. Normal battery life exceeds 200 hours for resistance measurements above 0.01 ohm.
* An external 2-volt storage battery or multiple 1.5-volt dry cells in parallel is recommended for prolonged measurements below 0.01 ohm.
* Alternative battery: Eveready 216 (NEDA 1604) with approximately 430 hours of battery life.

### Electrical

* **Measurement Method:** Four-terminal Kelvin Bridge method to eliminate lead and contact resistance errors.
* **Test Current:** Varies based on multiplier setting. For example, the Catalog No. 72-439 exhibits test currents ranging from 1.9 Amps for the 0.0001 to 0.0011 Ohm range up to 0.000065 Amps for the 10 to 110 Ohm range. The 72-432 is expected to operate similarly given its classification.

### Physical

* **Enclosure:** The 72-439 model features an aluminum top panel with a PVC acrylic plastic overlay and an ABS plastic case with a textured finish and hinged cover. The 72-432 is also described as portable.
* **Dimensions:**
* Catalog No. 72-439: 13″ x 9-1/4″ x 7″ high (33 x 23.5 x 17.8 cm).
* Catalog No. 72-436-01 (related model): 9″ x 7¾” x 7½” high (23 x 19 x 19 cm).
* **Weight:**
* Catalog No. 72-439: 15 lbs. (6.8 kg).
* Catalog No. 72-436-01: 5.5 lbs. (2.5 kg).

### Compatibility

* **Related Models:** The Biddle/AVO 72-432 is listed alongside the 72-430 model, which is identified as a Portable Wheatstone Bridge. This suggests a shared design philosophy and application focus.
* **Accessories:**
* Catalog No. 241005-5 Kelvin Clip Leads: 4 ft. long, with gold-plated jaws, insulated from each other, opening to ½”.
* Part No. 13098 Shielded Cable Assembly: Used for connecting the bridge to certain null detectors (e.g., Keithley 155).

### Manufacturer Information

Biddle Instruments, with a history dating back to 1895, is recognized as a leader in electrical test and measurement products. The company, often associated with AVO and MEGGER brands, offers a comprehensive range of instruments for field and laboratory use, serving various industries including electric utilities, large industrial facilities, and electrical apparatus manufacturing. Biddle Instruments operates a calibration lab traceable to NIST.

Why Choose Aumictech for Biddle/AVO 72-432?
At Aumictech, we specialize in supplying high-end electrical test and measurement equipment. Whether you need precise low resistance measurements for critical applications, reliable performance for field testing, or robust instruments for industrial environments, our team ensures the Biddle/AVO 72-432 delivers maximum performance for your application.