Something wrong in Fig. 1-16, page 24, Understading Signals

TenSongs

I wonder it is wrong to set up the trigger source with "none" for OPTAscope as shown in Fig. 1-16 on page 24, Understanding Signals. There are three trigger sources--CH1, CH2 and External. You can not choose any·trigger source other than this three.

PAR

TenSongs said...
I wonder it is wrong to set up the trigger source with "none" for OPTAscope as shown in Fig. 1-16 on page 24, Understanding Signals. There are three trigger sources--CH1, CH2 and External. You can not choose any·trigger source other than this three.

The "source" that is "none" is CH1. In other words, by selecting CH2 for example, then CH1 is not selected (it's "none").

Take a look at Fig. 1-17. In the upper righthand section of the scope, notice that "Channel Settings" is CH1, and that "Trigger Settings" is CH2 (in other words, CH1 trigger setting is "none"). Also, notice in the "Auto Measurements" section (upper right section of scope), it is "CH1" that is selected.

The wiring instructions tell you to connect the probe for CH1 to the signal to be observed.

I agree that the use of the term "none" in Fig. 1-16 is confusing. I believe the explanation above is the correct interpretation of what was intended. (If not, I'm sure someone else will correctly resolve the use of the term.)

PAR

TenSongs

Hi, Par

I see what you mean.
But take a look at Fig. 1-18, the trigger source is CH1 but Fig 1-19 shows the trigger setting is CH2. A discrepance!

If oscilloscope is run with what 'none' meant ( for example, using CH1 but setting CH2 for trigger source), you will find the signal roll on the screen.

I think if you are not using external trigger, your probe selecting and your trigger source setting must be of the same channel.

PAR

TenSongs said...
Hi, Par

I see what you mean.
But take a look at Fig. 1-18, the trigger source is CH1 but Fig 1-19 shows the trigger setting is CH2. A discrepance!

If oscilloscope is run with what 'none' meant ( for example, using CH1 but setting CH2 for trigger source), you will find the signal roll on the screen.

I think if you are not using external trigger, your probe selecting and your trigger source setting must be of the same channel.

On second look, I think you are right about the "none" term in Fig 1-16; it's the only such reference to "none" in the manual (and should probably be "CH1"). The "rolling" effect is due to the false triggering (on CH2) on the noisy signal of the unconnected CH2 probe (given the way the O-scope is configured --Fig 1-17, shown for that exercise-- which allows it to trigger on CH2).

(Incidentally, Fig 1-18 shows CH1 is the trigger, but again Fig 1-19 shows CH2 is set as the trigger. Later exercises get the setup and the O-Scope face correctly coordinated, e.g., Figs. 2-6, 2-7.)

PAR
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TenSongs

Hi, Par

I have another difficulty which seems getting no way to solve, I mean I posted this difficulty but get no response.

My difficulty is that CH2 probe can not be zero calibrated following the caliberating proceedure suggested by Parallax. As a result, whenever CH2 probe is plugged, the O-Scope will crush with a run time error '5' message appearing.

Is your CH2 OK or do you have any suggestion?

Thanks.

PAR

TenSongs said...
I have another difficulty which seems getting no way to solve, I mean I posted this difficulty but get no response.

My difficulty is that CH2 probe can not be zero calibrated following the caliberating proceedure suggested by Parallax. As a result, whenever CH2 probe is plugged, the O-Scope will crush with a run time error '5' message appearing.

Is your CH2 OK or do you have any suggestion?

My O-scope calibrates both channels. Both channels (1 and 2) work. My scope does not *crash*.
PAR