View source for DC504A

{{TM500 | mfg=Tektronix | type=DC504A | function=100 MHz, 6-digit frequency counter | class=counter | image=Tek dc504a.JPG  | introduced=1984 | discontinued=1993 |
designers= |manuals= 
* [[Media:070-4291-00.pdf|DC504A Manual]] (OCR)
}}
It replaced the [[DC504]].

{{BeginSpecs}}
{{Spec|Resolution           | 6 digits}}
{{Spec|Frequency Range      | DC (AC coupled: 10 Hz) to 100 MHz (rear interface 50 MHz) }}
{{Spec|Sensitivity          | 30 mV<sub>RMS</sub> sine wave to 100 MHz, 85 mV<sub>p-p</sub> pulse ≥5 ns }}
{{Spec|Input impedance      | 1 MΩ // 25 pF (rear interface 50 Ω) }}
{{Spec|Gate time            | 10 ms to 10 s in decade steps (autoranging 10 ms to 1 s) }}
{{Spec|Trigger Level Range  | ±2 V × attenuator setting }}
{{Spec|Totalize mode        | 1–999999 counts up to 10 MHz }}
{{Spec|Frequency Resolution | kHz ranges: 0.1 Hz; 1 Hz and 10 Hz (7 digit resolution possible in overflow kHz position); MHz ranges: 100 Hz, 1 kHz (9 digit resolution possible in overflow kHz position) }}
{{Spec|Period resolution    | ms ranges: 1 µs, 10 µs; s ranges: 10 ms, 1 ms, 0.1 ms}}
{{Spec|Display Time         | Variable  ~0.1 s ... ~10 s and HOLD mode}}
{{Spec|Time Base            | 10 MHz, ±1×10<sup>-7</sup>, ±5 ppm from 0°C to +50°C, ±1×10<sup>-6</sup> per year, Adjustable to within 5×10<sup>-8</sup>}}
{{EndSpecs}}

==Differences to DC504==
The DC504A adds a 6<sup>th</sup> display digit, extends the frequency range to 100 MHz, and single-shot resolution to 100 ns.
It adds autorange and averaging, and a PLL that multiplies frequencies from 10 Hz to 25 kHz by 100.

Unlike its predecessor, the DC504A has no digital outputs on the rear interface, only signal and clock inputs.  There is no int/ext front panel switch (replaced by an internal jumper), and no RPM mode/jumper.

==Links==
{{Documents|Link=DC504A}}
{{PatentLinks|DC504A}}

==Internals==
The DC504A is built around an [[Intersil ICM7226]] counter/7-segment driver IC.  The prescaler for 10−100 MHz is an [[MC10138]] ECL counter.  The ×100 PLL circuit uses a CD4046.

==Rear Interface==
* 16A − Signal input (GND on 17A)
* 14A − External Clock (GND on 15A)

==Pictures==
<gallery>
Tek dc504a.JPG            | DC504A
Tek dc504a front.jpg      | DC504A
DC504A_Left_Internal.jpg  | DC504A left internal
DC504A_Right_Internal.jpg | DC504A right internal
DC504A_3-4_View.jpg       | DC504A 3/4 view
</gallery>

==Components==
{{Parts|DC504A}}