IETLAB GenRad 1840-A Output Power Meter ( 0.1 mW ~ 20 watts)

(Full specifications can be found on datasheet)

-Power Range: 0.1 mW to 20 watts in five ranges, 40 Hz to 20 kHz; maximum rating is reduced by up to 50% (at 25 Hz), depending on impedance selected.
An auxiliary dB scale on the meter reads from -15 to +3 dB, referred to 1 mW.
Impedance Range: 0.6 Ω to 32 kΩ in two ranges; yielding 48 individual impedances spaced approximately 2 apart.
-Accuracy :
+Impedance:
at 1 kHz, ±6% max, -0.5% avg;
70 Hz to 2.5 kHz, ±7% above 10 kW;
70 Hz to 5 kHz, ±7% below 10 kW;
at 20 Hz, -15% max, -8% avg;
at 20 kHz, ±50% max, ±12% avg
+Power:
at 1 kHz, ±0.3 dB;
50 Hz to 6 kHz, ±0.5 dB;
30 Hz to 10 kHz, ±1 dB;
at 20 Hz, -1.5 dB max, -1 dB avg;
at 20 kHz, -5 dB max, ±1.5 dB avg.

Datasheet