| Q: What sizes must be known in order to determine the compatibility of an unknown probe? |
| A: - Equivalent circuit showing the pin assignment of the amplifier
- Load resistance of the amplifier input
- Sensitivity of the probe
- Frequency of the carrier frequency signal
- Amplitude of the carrier frequency signal
Excerpt from the catalog (section 1.1-7):
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| Q: Why are there problems with compatibilities? |
| A: Smaller manufacturers of measuring instruments often do not follow the specifications (compatibilities) of the original manufacturer. In many cases, they develop any solution that allows connection with the original probe. These input circuits are then different from the circuits of the original amplifier. Because the Mahr probes are not direct copies of the original probe this can lead to problems which are not experienced when using the original amplifiers.
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| Q: Can old cables from probe series 1300 and 1301 be reused? |
A: Old cables from series 1300 and 1301 cannot be reused because of the new VLDT converter. Nor can the new cables for the P2000 series be combined with the old probes. Using a new P2004 probe with old extension cables is likely to result in read-outs with only half the sensitivity. This is because a signal is only applied to Pin 2 and not to Pin 2 and 3, as should be the case.
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| Q: How is the measuring force defined? |
| A: The measuring force is always given in a horizontal position so that it is not influenced by the weight of the measuring bolt and stylus. The spring force of the bellows is always included in the calculations, apart from with a measuring force of 0.25 N. The bellows of the P2004 cause e.g. an additional measuring force of around 0.25 N. Therefore, the measuring force spring used for a measuring force of 0.25 N and 0.5 N is the same. With a measuring force of 0.5 N, only the measuring force of the installed bellows is added.
Measuring force springs can have relatively large force dispersions of around 20% depending on their manufacturing process.
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| Q: What types of pneumatic probe lifting / movement are used? |
| A: Mahr offers two types: xA Version probe lifting: The measuring bolt is extended under normal pressure and drawn in using underpressure. This requires a special Venturi nozzle which turns overpressure into underpressure. The xA Version differs from the standard version only in terms of the fitting for the air connection. The measuring force is exerted by the measuring force spring. The stronger the measuring force spring, the greater the underpressure needed to lift the probe. xB Version probe pressurization: The measuring bolt is retracted under normal pressure and has to be blown out using overpressure in order for measuring to take place. Unlike the standard probe and the xA Version, there is an extension spring rather than a pressure spring in the probe. The measuring force is determined by the strength of the overpressure. For the xB Version there is a diagram that shows the relationship between overpressure and measuring force both with and without bellows. |
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