OTC 4278 Hydraulic Flow Meter – 100 GPM 6000 PSI
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OTC 4278 (superseded by OTC 4278A) is a digital hydraulic flow meter for testing hydraulic circuits on industrial, construction, and agricultural equipment. It measures flow from 2.5 to 100 GPM at ±1% accuracy of indicated value, handles system pressure up to 6,000 PSI, and reads fluid temperature up to 250°F. Bi-directional turbine flow measurement plus a steel case and burst-disc overpressure protection make it shop-grade and field-durable.
Key Features
- Digital display for flow and temperature, analog gauge for pressure
- ±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 the valve
- Burst-disc overpressure protection prevents hydraulic fluid spillage
- Inner-pass system with extra burst discs included
- Larger display with service and battery indicators on the 4278A revision
- Powered by a single 9V battery (included)
Specifications
| Manufacturer | OTC Tools (Bosch Automotive Service Solutions) |
|---|---|
| Part Number | 4278 (superseded by 4278A) |
| Part Type | Hydraulic Flow Meter (Digital, Bi-Directional) |
| 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″-12 UN #16 SAE ORB |
| Dimensions | 7-7/8″ x 7-7/8″ x 9-29/64″ |
| Construction | Steel case |
| Power | 1 x 9V battery (included) |
| UPC | 731413581106 |
Cross References
This tool is identified by:
- OTC: 4278, 4278A (current revision)
- Bosch Automotive Service Solutions: 4278A
Applications
The 4278 / 4278A is used to test and diagnose hydraulic oil circuits across:
- Agricultural machinery — tractors, combines, loaders, implements
- Construction equipment — excavators, skid steers, backhoes, telehandlers
- Industrial hydraulic systems — presses, conveyors, manufacturing lines
- Mobile hydraulic equipment — utility trucks, boom lifts, forestry equipment
Use the meter to diagnose pump performance, check valve function, identify internal leaks, verify cylinder operation, and confirm hydraulic motor efficiency.
Related Products
- OTC 4277: 50 GPM Hydraulic Flow Meter — mechanical, 4–54 GPM range for smaller circuits
- OTC 4285: 100 GPM digital hydraulic flow test kit with built-in relief valves
OTC 4278A supersedes the original 4278 with a larger display and added service indicators. Both numbers refer to the same tool — orders for either ship the current 4278A.