Picoscope vs USB Autoscope Testing actuators


In this video, let’s have a look at measurements
of automotive actuators. Let’s start with simple measurements of control
signal from the gasoline injector. Both devices are connected to the control
signal terminal in the injector connector. In the USB Autoscope menu, Injector mode is
selected. Let’s choose the settings in the Pico menu. We observe the reference signal. We start the engine and we observe a signal
on the monitor at the same time. We watch this signal on the Pico monitor. Depending on the engine operating mode, the
pulse width varies. This is how this signal looks on the AUTOSCOPE
screen. In the continuous recording mode, the engine
start is clearly visible, idle mode, throttling. In the fuel restriction mode the pulses are
absent. Let’s compare the waveforms. They are exactly the same. We will measure the control signal of the
diesel injector of the Common Rail system. This signal is easily viewed with the help
of CTi-M current transducer that is included to the USB Autoscope kit. We choose necessary settings in the USB Autoscope
program. Similarly, we configure the Pico. Observe the reference signal. Start the engine. We observe injector control pulses. Both devices displayed them the same way. If needed, you can view these pulses in more
detail. On the USB Autoscope screen we see the engine start, idle mode, throttling, fuel supply restriction mode. If desired, these pulses can be zoomed and
viewed in more detail. The next measurement. This is a Variable Valve Timing system. To test this system, we need the signals from
crankshaft and camshaft sensors, ignition signal from the 1st cylinder,
VVT valve control signal. The ignition signal can be obtained using
the sync probe. The VVT valve control signal can be taken
using CTi-M current transducer. The oscilloscope probe is connected to the
VVT valve control signal wire. In the USB Autoscope menu, select CSS 4 channel
mode. In the Pico menu, select the Variable Valve
Timing mode. Oscilloscope probe is connected to the control
wire of the VVT valve. We see a reference waveform of the PWM valve
control signal. We start the engine and observe the signals. Pico showed that the PWM signal appeared in
the throttle mode. But the question is: how does the VVT controller
react to this? Is there really a timing adjustment? Indeed, the presence of a control signal on
the VVT valve does not mean that the system is working. After all, the VVT valve may be jammed or
VVT controller may be faulty or there may simply be a low oil pressure in the system. In all these cases, if there is a VVT valve
control signal, timing will not be adjusted. Thus, we see only pulses and not the process
of changing the valve timing. On the USB Autoscope screen, we see the signals
of the crankshaft sensor and camshaft sensor, sync signal and VVT valve control current. Here appear VVT valve control current of 1.8
Amps. Now we will use the automatic signal processing
software. We perform a special test. We specify necessary data. The efficiency graphs show that all cylinders
contribute almost the same. Turn on the test called “Phase”. It can be seen here that the VVT ​​system
worked only during the first throttling. Let’s consider how one of the camshaft sensor
pulses shifted in more detail. When the engine was idling, its leading edge
was 80 degrees before TDC of cylinder #1. Let’s look how this pulse looks on the waveform. At idle, a single pulse from camshaft sensor
is located opposite to the tooth gap of the crankshaft sensor signal. Now let’s check the position of the same pulse
of the camshaft sensor when the engine is running at high revs. It can be seen that now a single pulse of
the camshaft sensor signal is located before the tooth gap of the crankshaft sensor signal. The Phase tab shows that this pulse has shifted
from 80 to 110 degrees in front of TDC. This offset shows how the VVT system adjusted
the valve timing. To be continued…

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