OTC 4278 Hydraulic Flow Meter – 100 GPM 6000 PSI
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The OTC 4278 Hydraulic Flow Meter (superseded by OTC 4278A) is a professional-grade diagnostic tool for testing hydraulic flow circuits in industrial and agricultural machinery. It measures flow from 2.5 to 100 GPM with ±1% accuracy of indicated value, handles pressure up to 6,000 PSI, and monitors fluid temperatures up to 250°F. Protected by a durable steel case with electronic and fluid-filled gauges that dampen vibration for precise, reliable readings in demanding environments.
Key Features
- Digital display for flow and temperature with analog pressure gauge
- ±1% flow accuracy of indicated value; ±1.6% pressure accuracy of full scale
- Bi-directional flow measurement — reads flow in both directions, pressure on the high side of valve
- Standard burst disc protection system prevents hydraulic fluid spillage during overpressure events
- Inner pass system with extra burst discs included
- New larger display size with service and battery indicators (4278A revision)
- Requires 1 × 9V battery (included)
Specifications
| Manufacturer | OTC Tools (Bosch Automotive Service Solutions) |
|---|---|
| Part Number | 4278 (superseded by 4278A) |
| Part Type | Hydraulic Flow Meter |
| Flow Range | 2.5–100 GPM (10–400 LPM) |
| Flow Accuracy | ±1% of indicated value |
| Pressure Range | 0–6,000 PSI (0–420 bar) |
| Pressure Accuracy | ±1.6% of full scale |
| Temperature Rating | Up to 250°F |
| Inlet/Outlet Ports | 1-5/16"-12UN #16 SAE ORB |
| Dimensions | 7-7/8" × 7-7/8" × 9-29/64" |
| Construction | Steel case |
| Power | 1 × 9V battery (included) |
| UPC | 731413581106 |
Applications
The OTC 4278 hydraulic flow meter is used to test and diagnose hydraulic oil circuits in:
- Agricultural machinery — tractors, combines, loaders, implements
- Construction equipment — excavators, skid steers, backhoes
- Industrial hydraulic systems — presses, conveyors, manufacturing lines
- Mobile hydraulic equipment — utility trucks, boom lifts, forestry equipment
Use this meter to diagnose pump performance, check valve function, identify internal leaks, verify cylinder operation, and confirm motor efficiency across a wide range of hydraulic circuits.
Related Products
- OTC 4277: 50 GPM Hydraulic Flow Meter — mechanical, 4–54 GPM range for smaller circuits
- OTC 4285: Digital Hydraulic Flow Test Kit — 100 GPM with relief valves for comprehensive shop diagnostics
The OTC 4278A supersedes the original OTC 4278 with an updated larger display and service indicators. Both part numbers refer to the same tool family — if searching for OTC 4278A, this is the correct product.