Post Office Box Plug Type
Product Code : EL-EAE-10285
Quick Answer: Post Office Box Plug Type is a plug-type P.O. Box with sixteen non-inductive coils, two proportional arms and an infinity gap, available in 3-Ratio and 4-Ratio versions. It measures resistance between 0.1 and 1111000 ohms using a DC battery.
Last updated: October 2026
Key Features
- Sixteen non-inductive coils from 1 to 5000 ohms
- Two proportional arms: 10, 100, 1000 ohms (3-Ratio) or 1, 10, 100, 1000 ohms (4-Ratio)
- Infinity gap included
- Two spring keys for the battery and galvanometer
- Rectangular brass block, 12 mm & 14 mm thick
- Housed in a wood box
Technical Specifications
| Specification | Value |
|---|---|
| Versions | 3-Ratio and 4-Ratio |
| Coils | Sixteen, non-inductive: 1, 2, 2, 5, 10, 20, 20, 50, 100, 200, 200, 500, 1000, 2000, 2000, 5000 ohms |
| Proportional arms, 3-Ratio | Two arms, each with 10, 100, 1000 ohm coils |
| Proportional arms, 4-Ratio | Two arms, each with 1, 10, 100, 1000 ohm coils |
| Measuring range | 0.1 to 1111000 ohms, with a DC battery |
| Brass block | Rectangular, 12 mm & 14 mm thick |
| Accuracy, manganin coil | ±0.05% |
| Accuracy, constantan coil | ±0.1% |
| Keys | Two spring keys (battery and galvanometer) |
| Other | Infinity gap |
| Enclosure | Wood box |
About This Product
This Electrical And Electronics instrument measures resistance between 0.1 and 1111000 ohms with a DC battery and a galvanometer connected through its two spring keys. The 3-Ratio version has proportional arms of 10, 100 and 1000 ohms, while each arm of the 4-Ratio version also carries a 1 ohm coil. Boxes with manganin coils are rated ±0.05% and those with constantan coils ±0.1%.
Frequently Asked Questions
Q1. What is the difference between the 3-Ratio and 4-Ratio versions?
Both have sixteen coils. The 3-Ratio box has two proportional arms each with 10, 100 and 1000 ohm coils; the 4-Ratio box has arms each with 1, 10, 100 and 1000 ohm coils.
Q2. What range of resistance can the Post Office Box Plug Type measure?
Resistance between 0.1 and 1111000 ohms can be measured using a DC battery.
Q3. What accuracy is quoted?
±0.05% for boxes with manganin coils and ±0.1% for boxes with constantan coils.
Our export customers include schools, colleges and dealers in Gabon, Italy and Samoa.
Contact Lab Equipments Ambala for a quotation on the Post Office Box Plug Type.
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