11 of 11 people found the following review helpful.
By James Q. Smith
This family of hand-held digital scopes is reviewed with inconsistent quality and often misunderstood because of the hype in marketing. It was designed and released in 2002.
It can do 40 MS/s only when 8x oversampling its base 5 MS/s. This is not user selectable and switches automatically for repetitive waveforms, not transients. Using a rule of thumb of MSa/10= Freq Resp, the estimated useful frequency response of this scope is 500kHz-4 MHz, since the sampling determines how much aliasing errors one gets on a digital storage scope.
Its input amplifier rolls off -3dB at 12MHz but much less at lower input voltages, 5 MHz at 5mV/div. Since it uses an 8-bit CPU, its accuracy can't be better than 0.4%. These rules apply to other scopes as well, so their specs need to be derated from marketing hype.
This 'hobbyist' scope has features that rival far more expensive scopes and can be used seriously and professionally, if one knows its limitations.
Pros
Accuracy for price. I measured 0.5% throughout 0 to 60Vdc, <= 3% Vac and it can calculate frequency manually. I checked it usable frequency response to >= 3 MHz.
Storage scope: 2 samples can be stored, recalled, analyzed and optionally sent to PC via an old style RS232 serial port. See photos. All accessories to interface to a PC are included
Event monitor: slowest timebase allows capturing of over 24 hours worth of transient signals
Ergonomics: the scope is intuitive to use, and one can get going immediately, to a point
LCD: can be adjusted for optimal contrast and can easily be seen
AA power: easy to find, and the scope will slow charge installed NiMH
9-12V: it can use any generic brick adapter with the right plug
Accessories: travel case, probe, protective hand case, and RS232 cable are included
Durable and reliable: its been around since 2002, and reports of it breaking or acting erratically are nonexistent
Power consumption: measured, true to manual, 0.6mA when off, 160 mA ON, 240mA with backlight ON
Cons
Manual: All features are described but its not clearly written. The manual states it does 10 MS/s in single shot signals but the HPS40 will report 5 Ms/s, consistent with other sales literature from Velleman about its handheld scopes
LCD: Its pixels are dark purple, the background yellowish, rather than black pixels on white or silver common in modern LCDs. The contast on backlight becomes difficult to adjust when the battery's are weak, although it still usable via transmitted light; this is a key that the battery's need changing. Contrast and LCD size is good enough, but could be better. This is the single biggest drawback to this device.
Function Annunciators on the LCD: are tiny and unassuming, one has to learn to notice them
Ergonomics: some features are confusing. The molded icon above the ADJUST button does nothing. However, the other molded icons do mean something. The trigger button also stores waveforms into memory, if you press the MEMORY button first, which causes a HOLD icon to appear on the LCD. To recall the waveform, you press the t-V/div button, while toggles the waveform in memory and that visible on the screen at the time.
Keys: are rubbery and don't give solid tactile feedback. I'd rather it beep to insure the keypress was recognized
5 AA battery supply: odd. Since most chargers charge 2-4 AA at a time, having 5 available is inconvenient when finding sets of batteries to use. I use eneloop NiMH now, so I have a store of charged batteries for use anytime.
Safety: CAT II self-rated CE, not formally rated by UL, CSA, TUV etc.,
Conclusion:
This is a very good value scope at $200, find it at that price. A key use of this self-rated CAT II device is since its ground floats, there is little chance of destroying the scope when used for probing voltages that could fry a typical sensitive and more accurate chassis grounded mains powered scope, often rated CAT I. In one repair I made, spurious 600-1000Vdc spikes randomly appeared from a noisy defective switching power supply set at 300Vdc, the HPS40 read it and captured them using its slow timebase and its a probe set at 10x. Those inputs were at the limits of the safe input to the HPS40s amps with attentuation, but the spurious signals were far above the safe limits of my Rigol 50MHz DSO scope.
HPS 40 was previously priced near $400, at which point, it competes with other Chinese branded desktop/handheld scopes and it would less a good value, except for the HPS40's ultra portability and electrical isolation.
You can not get Price Compare Hand Held Digital Oscilloscope-40MHz with your qualification ? If you can't get anything from this suggestion, you can get another product from this store. You can check all product from this is store just click a label in below from this text.
0 comments:
Post a Comment