7A14: Difference between revisions
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{{Spec | Deflection | 1 mA/Div to 1 A/Div in 1–2–5 sequence }} | {{Spec | Deflection | 1 mA/Div to 1 A/Div in 1–2–5 sequence }} | ||
{{Spec | Bandwidth | P6021: 25 Hz – 50 MHz (55 MHz in [[7904|79xx]])<br />P6022: 250 Hz – 105 MHz (120 MHz in [[7904|79xx]], 80 MHz in [[7603|76xx]])}} | {{Spec | Bandwidth | P6021: 25 Hz – 50 MHz (55 MHz in [[7904|79xx]])<br />P6022: 250 Hz – 105 MHz (120 MHz in [[7904|79xx]], 80 MHz in [[7603|76xx]])}} | ||
{{Spec | Features | Bandwidth limiting switch (20 MHz), polarity switch}} | |||
{{EndSpecs}} | {{EndSpecs}} | ||
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===Measurement examples=== | ===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. <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>. | ||
====5 kHz Squarewave==== | ====5 kHz Squarewave==== | ||
Revision as of 02:10, 23 August 2023
The Tektronix 7A14 is a 120 MHz current probe amplifier vertical plug-in for 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 an adapter (s.b.)
The 7A14 is one of the original plug-in modules introduced at the start of the 7000 series in 1969.
Key Specifications
| Deflection | 1 mA/Div to 1 A/Div in 1–2–5 sequence |
|---|---|
| Bandwidth | P6021: 25 Hz – 50 MHz (55 MHz in 79xx) P6022: 250 Hz – 105 MHz (120 MHz in 79xx, 80 MHz in 76xx) |
| Features | Bandwidth limiting switch (20 MHz), polarity switch |
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. 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.
Links
Internals
The 7A14 uses twelve Tek-made miniature relays that can be a service issue.
The amplifier is an 8-stage discrete differential design. The plug-in contains no integrated circuits.
Prices
| Year | 1969 | 1974 |
|---|---|---|
| Catalog price | $575 | $700 |
| In 2022 Dollars | $4,600 | $4,200 |
Pictures
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7A14 front panel
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7A14, left side
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7A14, right side
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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.
The signal shown is a squarewave from a PG501 @ 4 Vp-p into 50 Ω = 80 mAp-p.
