Chapter 4
50 Mini-Convectron Module Instruction Manual - 275513
4.3 Convectron Gauge Test
Even a small amount of voltage can damage the small diameter sensing wire inside the Convectron
gauge.
To determine if the Convectron gauge sensing wire has been damaged, follow these instructions:
1. Remove the Convectron gauge as instructed in Section 4.4.1.
2. Use a low-voltage (maximum 0.1 V) ohmmeter to check resistance values across the pins on the
base of the gauge. Pin numbers are embossed on the base. Figure 4-1 illustrates the base of the
gauge.
The resistance across the pins should be within the ranges listed in Figure 4-1. If resistance across
pins 1 and 2 is not approximately 19 to 22 Ω, or if other listed resistance values are greater than the
listed values, the gauge is defective. Install a replacement Convectron gauge as instructed in Section
4.4.2.
Figure 4-1 Convectron Gauge Pins
Over-Pressure Conditions
Performing a Convectron gauge test with instruments that apply
more than 0.1 V with the gauge at vacuum chamber pressure
can result in property damage.
Do not perform a Convectron gauge test with an instrument that
applies more than 0.1 V of electromotive force.
• Pins 1 to 2: 19 to 22 ohms
• Pins 2 to 3: 50 to 60 ohms
• Pins 1 to 5: 180 to 185 ohms
If the resistance from pins 1 to 2 reads about 800
ohms, the sensor wire in the gauge is broken.
Replace the gauge tube.
Note: If the resistance values shown here are
correct, but you still think the gauge is not
reading correctly, the gold plating on the sensor
wire may be eroded and the gauge will have to
be replaced.
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