From ec8386b84b971f193de075d1ddc26902924eb35f Mon Sep 17 00:00:00 2001
From: Clement Remi <remi.clement@irstea.fr>
Date: Sat, 2 Apr 2022 19:12:17 +0200
Subject: [PATCH] Update Ohmpi.py, adding the auto gain fonction for a better
measurement of R
---
ohmpi.py | 36 ++++++++++++++++++++++++++++++++++--
1 file changed, 34 insertions(+), 2 deletions(-)
diff --git a/ohmpi.py b/ohmpi.py
index 0d3ce969..ce464b50 100644
--- a/ohmpi.py
+++ b/ohmpi.py
@@ -359,6 +359,19 @@ class OhmPi(object):
self.switch_mux(j, 'off', roles[i])
self.log_exec('All MUX switched off.', level='debug')
+ def gain_auto(self,channel):
+ gain=2/3
+ if ((abs(channel.voltage)<2.040) and (abs(channel.voltage)>=1.023)):
+ gain=2
+ elif ((abs(channel.voltage)<1.023) and (abs(channel.voltage)>=0.508)):
+ gain=4
+ elif ((abs(channel.voltage)<0.508) and (abs(channel.voltage)>=0.250)):
+ gain=8
+ elif abs(channel.voltage)<0.256:
+ gain=16
+ #print(gain)
+ return gain
+
def run_measurement(self, quad, nb_stack=None, injection_duration=None): # NOTE: quad not used?!
""" Do a 4 electrode measurement and measure transfer resistance obtained.
@@ -392,6 +405,25 @@ class OhmPi(object):
pin1.direction = Direction.OUTPUT
pin0.value = False
pin1.value = False
+
+ # FUNCTION AUTOGAIN
+ # ADS1115 for current measurement (AB)
+ self.ads_current = ads.ADS1115(self.i2c, gain=2/3, data_rate=860, address=0x48)
+ # ADS1115 for voltage measurement (MN)
+ self.ads_voltage = ads.ADS1115(self.i2c, gain=2/3, data_rate=860, address=0x49)
+ # try auto gain
+ pin1.value = True
+ pin0.value = False
+ time.sleep(injection_duration)
+ gain_current=self.gain_auto(AnalogIn(self.ads_current,ads.P0))
+ gain_voltage=self.gain_auto(AnalogIn(self.ads_voltage,ads.P0,ads.P1))
+ pin0.value = False
+ pin1.value = False
+ print(gain_current)
+ print(gain_voltage)
+ self.ads_current = ads.ADS1115(self.i2c, gain=gain_current, data_rate=860, address=0x48)
+ self.ads_voltage = ads.ADS1115(self.i2c, gain=gain_voltage, data_rate=860, address=0x49)
+
# TODO I don't get why 3 + 2*nb_stack - 1? why not just rnage(nb_stack)?
# or do we consider 1 stack = one full polarity? do we discard the first 3 readings?
@@ -412,9 +444,9 @@ class OhmPi(object):
for k in range(0, self.nb_samples):
# reading current value on ADS channel A0
meas[k, 0] = (AnalogIn(self.ads_current, ads.P0).voltage*1000) / (50 * self.r_shunt)
- meas[k, 1] = AnalogIn(self.ads_voltage, ads.P0).voltage * self.coef_p2 * 1000
+ meas[k, 1] = AnalogIn(self.ads_voltage, ads.P0, ADS.P1).voltage * self.coef_p2 * 1000
# reading voltage value on ADS channel A2
- meas[k, 2] = AnalogIn(self.ads_voltage, ads.P1).voltage * self.coef_p3 * 1000
+ #meas[k, 2] = AnalogIn(self.ads_voltage, ads.P1).voltage * self.coef_p3 * 1000
# stop current injection
pin1.value = False
--
GitLab