Modern digital multimeters provide excellent accuracy, but they have a limited bandwidth often in the range of a few kHz. They also provide only ac rms, meaning they are unable to fully quantify complex waveforms for peak, total rms, dc level and other parameters. 

Engineers naturally turn to oscilloscopes and probes to make rms and peak measurements in the higher frequency region.Oscilloscopes are excellent diagnostic tools for viewing waveforms, but the accuracy at higher frequency is best described as an indication, especially when combined with external probes. The absence of laboratory accuracy is a result of compromises that have to be made in creating devices that can handle very wide bandwidths of 50 MHz or more . Stray capacitance, inductance, skin effect, slew rate, gain bandwidth limits, high speed ADC sampling and resolution make it difficult if not impossible to maintain the kind of accuracy we expect from a modern digital multimeter. 

In practice, users can reasonably assume an accuracy of ±3% to ±5% for measurements above 1kHz, provided the compensation for any external probes have been carefully adjusted. This assumed accuracy is fine for many applications, but there will be times when greater accuracy or confidence is desired. The HFTEQ range of equipment is designed to fit this need, maintaining high accuracy up to 1MHz.   

There are several other reasons why HFTEQ range may be useful. 

One key point is to make the measurement traceable - many probes and even oscilloscopes use a different operating mode and even different components to handle higher frequency region, meaning that calibration at DC or low frequency is irrelevant to measurements at high frequency. Of equal concern is knowing if the probes have been properly adjusted and have a reasonably flat frequency response. Random samples from various third party laboratories and manufacturer sites have found that often probes are not adjusted, and that certain brands or types have very high variations with frequency. 

Manufacturers making measurements in a regulatory or legal context, and accredited third party laboratories should not be relying on measurements at high frequency unless the equipment and the set up has been validated at the frequencies of interest. Users can select either a HFTEQ high frequency voltmeter to monitor the true rms and peak voltages; or the HF Calibrator which produces a precise voltage over a broad range of frequencies, and can be used to validate individual set ups at the frequency of interest. 

Another reason is that oscilloscope settings need to be made carefully in order to measure peak and rms values correctly. The sample rate needs to be high enough to capture the true peak and enough detail of the waveform for rms calculations, but at the same time the the device needs to capture enough cycles of the waveform such that partial cycles do not unduly influence the result. The HFTEQ range responds to the true rms value regardless of the underlying waveform (from 50Hz to 1MHz). 

Finally is the problem that genuinely floating measurements are often not possible with oscilloscopes. The potential for stray leakage paths and other effects can have large effects at high frequency.  The HFTEQ meter is floating, relatively small and can be connected into the circuit with short leads to minimize the influence.   

The HFTEQ range of equipment targets a more moderate frequency range of just 1MHz, but with the advantage of being able to maintain highly accurate and traceable measurements in that region. The measurement method is the same from 50Hz to 1MHz, and the design has a flat, simple first order response up to the 3dB point of 11MHz. The range of "laboratory reference" meters are specially designed to use only resistive dividers with stray parameters calculated and tested to confirm the 11MHz bandwidth. The equipment is intrinsically accurate and needs no adjustment on assembly.

HFTEQ equipment is not intended to completely replace oscilloscopes, as engineers will always want to view the waveforms. Rather the HFTEQ is intended as a supplement scopes and probes where reliable, accurate measurements are necessary or can improve the quality of decisions.