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7A14: Difference between revisions
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|summary=120 MHz current probe amplifier | |summary=120 MHz current probe amplifier | ||
|image=Tek 7a14 de.jpg | |image=Tek 7a14 de.jpg | ||
|caption=7A14 | |caption=Tektronix 7A14 | ||
|introduced=1969 | |introduced=1969 | ||
|discontinued=1975 | |discontinued=1975 | ||
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The '''Tektronix 7A14''' is a 120 MHz current probe amplifier vertical plug-in for [[7000-series scopes|7000 series]], intended to be used with passive current probes such as the [[P6021]] and [[P6022]]. | The '''Tektronix 7A14''' is a 120 MHz current probe amplifier vertical plug-in for [[7000-series scopes|7000 series]], intended to be used with passive current probes such as the [[P6021]] and [[P6022]]. | ||
The [[P6019]] and [[P6020]] also work but with reduced bandwidth flatness, and the P6019 needs | The [[P6019]] and [[P6020]] also work but with reduced bandwidth flatness, and the [[P6019]] needs a [[131-0750-00]] adapter (s.b.) | ||
The 7A14 is one of the original plug-in modules [[introduced in 1969|introduced at the start of the 7000 series in 1969]]. | The 7A14 is one of the original plug-in modules [[introduced in 1969|introduced at the start of the 7000 series in 1969]]. | ||
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==Operation== | ==Operation== | ||
In the 7A14, the ring around the input [[BNC connector]] that is used to identify ×10/×100 probes on voltage probes serves the purpose of detecting the difference between the P6021 and P6022 probes, and switching in appropriate gain and frequency compensation. | In the 7A14, the ring around the input [[BNC connector]] that is used to identify ×10/×100 probes on voltage probes serves the purpose of detecting the difference between the [[P6021]] and [[P6022]] probes, and switching in appropriate gain and frequency compensation. | ||
The P6021 shorts this ring to ground, directly switching three relays connected to −15 V internally. When connecting a [[P6019]] probe, the ring must also be grounded but the probe connector does not have the matching pin. The [[131-0750-00]] adapter solves this problem. | The [[P6021]] shorts this ring to ground, directly switching three relays connected to −15 V internally. When connecting a [[P6019]] probe, the ring must also be grounded but the probe connector does not have the matching pin. The [[131-0750-00]] adapter solves this problem. | ||
The front panel gain and low frequency compensation screwdriver adjustments do not differentiate between the P6021 or P6022 probes, i.e. swapping probes requires re-adjustment. Note that the low frequency compensation adjustment has a large impact on waveform accuracy and requires careful adjustment to a certain slope when using a 1 kHz calibrator signal as discussed in the manual. | The front panel gain and low frequency compensation screwdriver adjustments do not differentiate between the [[P6021]] or [[P6022]] probes, i.e. swapping probes requires re-adjustment. Note that the low frequency compensation adjustment has a large impact on waveform accuracy and requires careful adjustment to a certain slope when using a 1 kHz calibrator signal as discussed in the manual. | ||
==Links== | ==Links== | ||
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==Internals== | ==Internals== | ||
The 7A14 uses twelve Tek-made [[miniature relays]] that can be a service issue. | The 7A14 uses twelve Tek-made [[miniature relays]] that can be a service issue. | ||
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==Pictures== | ==Pictures== | ||
<gallery> | <gallery> | ||
Tek 7a14 1.jpg | Tek 7a14 1.jpg | ||
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</gallery> | </gallery> | ||
==Measurement examples== | |||
Current through a 50 Ω resistor measured with [[P6021]] (top trace) compared to the voltage across the resistor (bottom trace). Measured with [[7854]] and [[7A26]] illustrating the low frequency limitation of the different probe termination methods. In the 10 mA/mV setting of the termination box the gain of the scope's vertical amplifier is insufficient to scale the current trace to the same nominal size as the voltage trace. <br /> | Current through a 50 Ω resistor measured with [[P6021]] (top trace) compared to the voltage across the resistor (bottom trace). Measured with [[7854]] and [[7A26]] illustrating the low frequency limitation of the different probe termination methods. In the 10 mA/mV setting of the termination box the gain of the scope's vertical amplifier is insufficient to scale the current trace to the same nominal size as the voltage trace. <br /> | ||
The signal shown is a squarewave from a [[PG501]] @ 4 V<sub>p-p</sub> into 50 Ω = 80 mA<sub>p-p</sub>. | The signal shown is a squarewave from a [[PG501]] @ 4 V<sub>p-p</sub> into 50 Ω = 80 mA<sub>p-p</sub>. | ||