Testo 0638 1557 External Vacuum Probe for Testo 557

The Testo 0638 1557 is an external vacuum probe designed specifically for the Testo 557 digital manifold, delivering faster and more reliable evacuation measurements than the manifold's internal sensor alone. With a measurement range of 0 to 20,000 microns and 1-micron resolution at the critical low end, it gives HVAC technicians the precision needed to confirm a proper deep vacuum before charging.

Key Specifications

• Measurement range: 0 to 20,000 microns
• Accuracy: ±(10 micron + 10% of reading) from 100 to 1,000 microns
• Resolution: 1 micron (0–1,000 micron) | 10 micron (1,000–2,000) | 100 micron (2,000–5,000) | 500 micron (5,000–10,000) | 5,000 micron (10,000–20,000)
• Compatible with: Testo 557 digital manifold
• Connection: Secure, reliable probe connection for all refrigeration systems and heat pumps

Why Use an External Vacuum Probe?

Placing the vacuum sensor at the system rather than at the manifold eliminates hose volume from the measurement, giving a true reading of the system vacuum. This is critical for accurate evacuation verification on split systems, ducted systems, and commercial refrigeration circuits.

Related Products

Browse all Testo HVAC instruments and digital manifolds at HVAC Supply Shop, or explore our full range of HVAC service tools.

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