If Keysight Marketing is collecting feedback on the oscilloscopes, I am adding here some notes about the desired features of the instruments I wish to find in my lab.
The major capabilities of recent scopes are stable and are commodity, but, in addition is expected to have following features:
· Galvanic isolation of the signal ground from power ground and/or ability to run off removable, optional battery of 12V external battery. It is needed for measurements in switch-mode power supplies, non-isolated devices, and also to significantly reduce the ground-loop induced noise which in my lab may reach 10-50mV p-p.
· Large screen, ideally with capacitive touch. 8-9” as in mainstream tablets.
· Sampling rate at least 500MHz per channel in all acquisition modes. The number of analog channels 2 (minimum), bit 4 channels is more practical and is available on competitive entry level scopes. Analog bandwidth 125MHz (min) or better. 8-bit ADC minimum, 10-bit preferred, 8bit ENOB
· At least 8 LVCMOS digital inputs, included in capture. 16 -18 channels preferred. Ideally, these channels should have a level translator chip in the input or in the probe, with the selection of Vcc of 1.0, 1.2, 1.8, 2.5, 3.3V logic levels. The lowest cost and most feasible solution would put the level translator in the probe, and allow users to build other level translators (for instance, for differential formats like LVDS/RS485, PECL, etc.). The user may also connect FPGA-based pod for application-specific enhancement. The connector pinout should be open specification and contain clock, signals and power.
· Memory depth for simultaneous acquisition- with current high speed DRAMs, it is not too expensive to have at least 16M samples, and low cost competition currently ships 25M samples standard. The memory should include ADC samples, trigger channel and logic channels. The data transfer to PC should run in binary.
· External and logic trigger in addition to standard analog, TV and glitch triggering.
· Ethernet and USB for data communication, VISA support, data converter to standard Windows WAV format and open internal format specification
· Automatic probe multiplier detection through resistance/ring. These probes are widely available and pretty standard, and it will be very convenient to scale display appropriately. X2, x 5, x10 and x50 probes should be supported. OK to not read calibration data from probes.
· Display with time base, X/Y in dot and vector format (may be some restrictions on vector format rendering speed – OK). Hardware lookup for display in linear and logarithmic (dB) scale. Infinite persistence, averaging and peak values display (for displaying signal envelopes).
· Math on channels to display three traces in a group of two channels – A, B, A-B together for signals with ternary encoding and embedded clocks.
· Math function to display phase and amplitude of the signals when captured on two channels, one source and one reference. Nice to have computation/display of the amplitude SQRT(A^2+B^2) and phase. Display peak values on amplitude trace.
· Single button configuration (all settings) recall from non-volatile memory. The control panels today have too many multi-function controls, the user should be able to set up the configuration and store it for future quick access. Need at least 10-16 setting sets for store/recall
· Nice to have equivalent time mode. Horizontal modes: normal, roll, X/Y.
· Easy single function buttons for normal, auto, single modes. Good rotary encoders – in most of my scopes, the knob encoders are the weakest point and poor contacts make scopes unusable.
· Low-cost active probes with 100-200MHz bandwidth. There are many cheap buffer amplifiers available (like LMH6559), having low-noise, high impedance active probes even in 100MHz scope is significant plus for working with today’s designs. Fine pitch grabbers as an option. Great to have light (LED) in the probe. Such probes can be sold as extras.
· Connector for USB Keyboard and mouse – it is very difficult to enter filenames for USB storage. Alternative – Bluetooth interface for smart phone which can be used as keyboard
· Fast risetime calibrator output – 0.5V in 50 Ohm. 200ps rise time/fall time (eg, PECL), configurable frequency – 1kHz, 100kHz, 1MHz even in low cost entry scope for checking channel rise/fall times. This output should be also configurable as trigger output to accurately synchronize other instruments.
Expandable MSO Concept
The entry level analog scopes are usually not sufficient for complex digital design, and a combination of logic analyzer and analog scope is desirable. Such combination, though, may not be sufficient for advanced users, interested in working with complex protocols and decoding or cross triggering on them.
The solution may be described as “Smart Pod” where a probe pod is connected with the main scope unit with flexible, high speed serial cable (in a formfactor of USB3.2 or HDMI). Within a pod, an entry level FPGA is located. The FPGA is loaded from the scope where the configuration files may be developed by the user and uploaded to the scope through VISA.
The function of FPGA is to support level shifting and different logic level standards, and data aggregation, serial to parallel protocol conversion and trigger condition generation from protocols and user defined state machines. The scope vendor should supply several pre-built configuration files for standard protocols.
The users or vendor may upgrade the configurations later in the field.
More details on the concept here.