Voltage Measurements
Single datapoints¶
get_voltage : Measure voltage¶
Reads voltage from specified channel , and returns the value.
Autorange is enabled for this function, and it automatically selects the appropriate voltage range if either A1, or A2 are specified
| parameter | description |
|---|---|
| Channel | Analog input to measure. A1,A2,A3, MIC, SEN, or IN1 |
| return | Voltage from chosen input |
x = p.get_voltage(‘A1’)
import eyes17.eyes
p = eyes17.eyes.open()
print ('Voltage between A1 and GND = ',p.get_voltage('A1'))
print (p.get_voltage('A2'))
print (p.get_voltage('A3'))
get_voltage_time : Measure voltage with a timestamp¶
Reads voltage from specified channel , and returns the timestamp and measured value. Return T,V
t, v = p.get_voltage_time()
print(f'Measured V:{v} , at T:{t}')
get_average_voltage : Makes and returns average of n readings¶
v = p.get_average_voltage(samples=50) #Keyword argument samples. default=10 if omitted
print(f'Measured V:{v}')
voltmeter_autorange¶
Takes a few readings and expands/contracts the voltage range till the value is comfortably within the range.
range selection is done by calling the select_range function described later.
This function is invoked by the get_voltage, and get_voltage_time functions
and does not need to be called separately.
p.voltmeter_autorange()
Code Example : Diode IV Characteristics
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
voltage = []
current = []
v = 0.0
while v <= 5.0:
va = set_pv1(v)
vd = get_voltage('A1')
i = (va-vd)/1.0 # current in milli Amps
voltage.append(vd)
current.append(i)
v = v + 0.050 # 50 mV step
xlabel('Voltage')
ylabel('Current')
plot(voltage, current, linewidth = 2)
show()
Multiple, Equidistant voltage acquisition: Synchronous routines¶
These calls initiate an oscilloscope acquisition process, and wait for it to complete before returning the data in the form of arrays.
Warning
These calls are blocking, and are not recommended in interactive graphical programs if you intend to record for periods longer than 100mS
capture1 : Single Channel Oscilloscope¶
Blocking call that fetches oscilloscope traces from any analog input A1,A2,A3, MIC, SEN, or IN1
| parameter | description |
|---|---|
| Channel | Analog input to measure. A1,A2,A3, MIC, SEN, or IN1 |
| ns | Number of samples to fetch. Maximum 2500 |
| tg | Timegap between samples in microseconds. Minimum 1.75uS |
| return | Arrays X(timestamps),Y(Voltages from chosen input) |
x,y = p.capture1(‘A1’,500,10)
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
x,y = p.capture1('A1',500,10)
plot(x,y)
show()
capture_action : Single Channel Oscilloscope with digital state control¶
Blocking call that records and returns an oscilloscope trace from the specified input channel after executing another command such as SET_LOW,SET_HIGH,FIRE_PULSE etc on SQ1
| parameter | description |
|---|---|
| Channel | Analog input to measure. A1,A2,A3, MIC, SEN, or IN1 |
| ns | Number of samples to fetch. Maximum 2500 |
| tg | Timegap between samples in microseconds. Minimum 1.75uS |
| *args | SET_LOW : set OD1 low before capture |
| SET_HIGH : set OD1 high before capture | |
| FIRE_PULSE : make a high pulse on OD1 before capture. | |
| Use keyword argument pulse_width = x,where x = width of the pulse in uS. default width =10uS | |
| Use keyword argument pulse_type = ‘high_true’ or ‘low_true’ to decide type of pulse | |
| x,y = p.capture_action(‘A1’,2000,1,’FIRE_PULSE’,interval = 250) #Output 250uS pulse on OD1 before starting acquisition | |
| SET_STATE : change Digital output immediately after capture starts. | |
| Use keyword arguments that will be forwarded to the set_state command | |
| return | Arrays X(timestamps in mS),Y(Voltages from chosen input) |
x,y = p.capture_action(‘A1’,500,10, ‘SET_LOW’)
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
x,y = p.capture_action('A1',2000,1,'SET_LOW') #set OD1 LOW before starting acquisition
plot(x,y)
show()
RL Transient Experiment
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
import time
plt.plot([0,.5], [0,0], color='black')
plt.ylim([-5,5])
p.set_state(OD1=1) # OD1 to HIGH
time.sleep(.5)
t,v = p.capture_action('A1', 100, 5, 'SET_LOW')
plt.plot(t,v,linewidth = 2, color = 'red')
plt.show()
RC Transient Experiment
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
import time
p.set_state(OD1=0) # OD1 to LOW
time.sleep(.5)
t,v = p.capture_action('A1', 100, 5, 'SET_HIGH')
plt.plot(t,v,linewidth = 2, color = 'blue')
p.set_state(OD1=1) # OD1 to LOW
time.sleep(.5)
t,v = p.capture_action('A1', 100, 5, 'SET_LOW')
plt.plot(t,v,linewidth = 2, color = 'red')
plt.show()
capture2 : 2 Channel Oscilloscope¶
Blocking call that fetches oscilloscope traces from A1,A2,A3,MIC .
| parameter | description |
|---|---|
| ns | Number of samples to fetch. Maximum 2500 |
| tg | Timegap between samples in microseconds. Minimum 1.75uS |
| TraceOneRemap | Analog input for channel 1. It is connected to A1 by default.Channel 2-4 always reads CH2-MIC |
| return | Arrays X1(timestamps in mS),Y1(Voltage at A1),X2(timestamps in mS),Y2(Voltage at A2),X3(timestamps in mS) |
t,v1,t2,v2 = p.capture2(1000,2)
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
p.set_sine(200)
t,v, tt,vv = p.capture2(500, 20) # captures A1 and A2
xlabel('Time(mS)')
ylabel('Voltage(V)')
plot([0,10], [0,0], 'black')
ylim([-4,4])
plot(t,v,linewidth = 2, color = 'blue')
plot(tt, vv, linewidth = 2, color = 'red')
show()
AC-DC Separating Demonstration
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
set_sqr1(200)
select_range('A1',8)
select_range('A2',8)
t,v, tt,vv = capture2(500, 20) # captures A1 and A2
plt.xlabel('Time(mS)')
plt.ylabel('Voltage(V)')
plt.plot([0,10], [0,0], 'black')
plt.ylim([-6,6])
plt.plot(t,v,linewidth = 2, color = 'blue')
plt.plot(tt, vv, linewidth = 2, color = 'red')
plt.show()
Diode Clamping Experiment
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
p.set_sine(200)
p.set_pv1(1.7) # will clamp at 2.0 + diode drop
maxV = 8
p.select_range('A1', maxV)
p.select_range('A2', maxV)
t,v, tt,vv = p.capture2(500, 20) # captures A1 and A2
plt.xlabel('Time(mS)')
plt.ylabel('Voltage(V)')
plt.plot([0,10], [0,0], 'black')
plt.ylim([-maxV, maxV])
plt.plot(t,v,linewidth = 2, color = 'blue', label='Input')
plt.plot(tt, vv, linewidth = 2, color = 'red', label='Clamped')
plt.legend(framealpha=0.5)
plt.show()
capture4 : 4 Channel Oscilloscope¶
Blocking call that fetches oscilloscope traces from A1,A2,A3,MIC .
| parameter | description |
|---|---|
| ns | Number of samples to fetch. Maximum 2500 |
| tg | Timegap between samples in microseconds. Minimum 1.75uS |
| TraceOneRemap | Analog input for channel 1. It is connected to A1 by default.Channel 2-4 always reads CH2-MIC |
| return | Arrays X1(timestamps in mS),Y1(Voltage at A1),X2(timestamps in mS),Y2(Voltage at A2),X3(timestamps in mS),Y3(Voltage at A3),X4(timestamps in mS),Y4(Voltage at MIC) |
t,v1,v2,v3,v4 = p.capture4(1000,2)
from matplotlib import pyplot as plt
I=eyes17.Interface()
x1,y1,x2,y2,x3,y3,x4,y4 = I.capture4(800,1.75)
plot(x1,y1)
plot(x2,y2)
plot(x3,y3)
plot(x4,y4)
show()
capture1_hr : Single Channel Oscilloscope.¶
Blocking call that fetches oscilloscope traces from any analog input A1,A2,A3, MIC, SEN, or IN1
with higher resolution (12-bit).
| parameter | description |
|---|---|
| Channel | Analog input to measure. A1,A2,A3, MIC, SEN, or IN1 |
| ns | Number of samples to fetch. Maximum 2500 |
| tg | Timegap between samples in microseconds. Minimum 1.75uS |
| return | Arrays X(timestamps),Y(Voltages from chosen input) |
x,y = p.capture1_hr(‘A1’,500,10)
import eyes17.eyes
p = eyes17.eyes.open()
from matplotlib import pyplot as plt
x,y = p.capture1_hr('A1',500,10)
plot(x,y)
show()
Configuration options¶
configure_trigger¶
configure_trigger(chan, name, voltage, resolution=10, **kwargs)
configure trigger parameters for capture commands The capture routines will wait till a rising edge of the input signal crosses the specified level. The trigger will timeout within 8mS tops, and capture routines will start regardless.
These settings will not be used if the trigger option in the capture routines are set to False
| parameter | description |
|---|---|
| chan | channel . 0,1,2,3. corresponding to the channels being recorded by the capture routine(not the analog inputs) |
| name | the name of the channel. ‘A1’… ‘SEN’ |
| voltage | Voltage level for triggering |
Example code for triggering on A1 at 1.1V threshold in single capture mode
p.configure_trigger(0,'A1',1.1)
Example code for triggering on A2 at 0V threshold in double capture mode
p.configure_trigger(1,'A2',0)
select_range¶
select_range(channel, voltage_range)
set the gain of the selected channel. Only for A1 and A2 inputs which have programmable gain amplification available.
| parameter | description |
|---|---|
| channel | A1 or A2 |
| voltage_range | choose from analogRanges.keys() [16,8,4,2.5,1.5,1,.5,.25] |
Example code for setting A1 full scale range to ± 4 Volts
p.select_range('A1',4)
Multiple, Equidistant voltage acquisition: Asynchronous routines¶
This sections lists separate function calls available for
- instructing the hardware to initiate a capture process
- Querying for the number of samples collected at any time
- Fetching the data buffer either intermittently, or when the acquisition is over.
capture_traces: Initialize the Oscilloscope¶
capture_traces(num, samples, tg, channel_one_input='A1', CH123SA=0, **kwargs)
Instruct the device to start recording data from 1 / 2 / 4 channels simultaneously. use fetch_trace to retrieve the data.
| parameter | description |
|---|---|
| num | Channels to acquire. ½/4 |
| samples | Total points to store per channel. Maximum 3200 total. |
| tg | Timegap between two successive samples (in uSec) |
| channel_one_input | map channel 1 to ‘A1’ … ‘SEN’ |
| **kwargs | |
| *trigger | Whether or not to trigger the oscilloscope based on the voltage level set by configure_trigger |
- Channel 1 can be mapped to any analog input
A1,A2,A3, MIC, SEN, or IN1 - Channel 2 is A2
- Channel 3 is A3
- and Channel 4 is MIC.
oscilloscope_progress: Fetch status of the Oscilloscope¶
oscilloscope_progress
returns the number of samples acquired by the capture routines, and the conversion_done status
| parameter | description |
|---|---|
| return | conversion done(bool) , waiting_for_trigger(bool), samples acquired (number) |
fetch_trace: retrieve collected data buffers¶
x,y = fetch_trace(channel_number)
returns the number of samples acquired by the capture routines, and the conversion_done status
| parameter | description |
|---|---|
| channel_number | 1 , 2, 3, or 4. For a single channel capture, use fetch_trace(1). for multiple channels, use fetch_trace(1),… fetch_trace(4) |
| return | X(list of timestamps in uS) , Y (list of voltages in Volts) |
Example code for initializing capture, waiting for completion, and reading the data
import time
# Init Single Channel Acquisition. 500 samples with 10uS gap each.
p.capture_traces(1, 500, 10, 'A1', trigger=False)
time.sleep(1e-6 * 500 * 10 + .01)
while 1:
x = p.oscilloscope_progress()
print('conversion done : %d, triggered:%d ,samples acquired: %d'%(x[0],x[1],x[2]))
if x[0]: break
time.sleep(0.01)
#Read the data.
x, y = p.fetch_trace(1)