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bug fix
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‎Keithley_6517B/High_Resistance/Backends/IV_K6517B_Simple_Backend_v10.py‎

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'''
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===============================================================================
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PROGRAM: Keithley 6517B I-V Sweep Measurement
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PURPOSE: Perform a voltage sweep and measure current to generate an I-V
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curve using a Keithley 6517B.
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DESCRIPTION: This script automates an I-V sweep measurement using a Keithley
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6517B electrometer. It prompts the user for sweep parameters
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(start/stop voltage, steps, delay), performs a zero-check
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correction, executes the voltage sweep while measuring current,
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saves the data to a CSV file, and displays a plot of the
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resulting I-V curve.
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AUTHOR: Prathamesh Deshmukh
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GUIDED BY: Dr. Sudip Mukherjee
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INSTITUTE: UGC-DAE Consortium for Scientific Research, Mumbai Centre
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VERSION: 5.1
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LAST EDITED: 04/10/2025
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===============================================================================
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'''
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#-------------------------------------------------------------------------------
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# Name: Keithley 6517B electrometer
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# Purpose: Current Measurement Backend
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# Author: Prathamesh K Deshmukh
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# Created: 03-03-2024
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# Updates: V1.3 (Fixed DataFrame saving bug)
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#-------------------------------------------------------------------------------
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import time
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import csv
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import numpy as np
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import matplotlib.pyplot as plt
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from datetime import datetime
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try:
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from pymeasure.instruments.keithley import Keithley6517B
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from pyvisa.errors import VisaIOError
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except ImportError:
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print("Error: Required packages not found.")
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print("Please install them by running: pip install numpy matplotlib pymeasure")
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exit()
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# --- 1. USER CONFIGURATION ---
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# The VISA address is fixed as it was in V5.
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VISA_ADDRESS = "GPIB1::27::INSTR"
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def get_sweep_parameters():
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"""Gets I-V sweep parameters from the user."""
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print("--- I-V Sweep Configuration ---")
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start_v = float(input("Enter Start Voltage (V): "))
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stop_v = float(input("Enter Stop Voltage (V): "))
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steps = int(input("Enter Number of Steps: "))
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delay = float(input("Enter Settling Delay between points (s): "))
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filename = input("Enter the filename to save data (e.g., SampleA_IV.csv): ")
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if not filename.lower().endswith('.csv'):
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filename += '.csv'
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return start_v, stop_v, steps, delay, filename
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def plot_results(data):
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"""Plots the I-V curve from the collected data."""
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if not data:
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print("\nNo data to plot.")
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return
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voltages = [float(row[1]) for row in data]
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currents = [float(row[2]) for row in data]
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plt.figure(figsize=(8, 6))
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plt.plot(voltages, currents, 'o-', label='I-V Data', color='#003f5c')
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plt.title('I-V Measurement Curve', fontsize=16)
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plt.xlabel('Applied Voltage (V)', fontsize=12)
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plt.ylabel('Measured Current (A)', fontsize=12)
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plt.grid(True, which="both", ls="--", alpha=0.6)
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plt.ticklabel_format(style='sci', axis='y', scilimits=(0,0))
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plt.legend()
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plt.tight_layout()
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print("\nDisplaying I-V plot...")
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plt.show()
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import pandas as pd
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import pyvisa
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from pymeasure.instruments.keithley import Keithley6517B
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# --- Main Execution ---
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keithley = None
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results = []
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I = []
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t = []
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try:
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# Get sweep parameters from the user
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start_v, stop_v, steps, delay, filename = get_sweep_parameters()
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voltage_sweep = np.linspace(start_v, stop_v, steps)
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# Initialize Instrument
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keithley = Keithley6517B("GPIB0::27::INSTR")
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time.sleep(0.5)
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# Setup Measurement
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keithley.measure_current()
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time.sleep(0.5)
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print("Starting measurement... Press Ctrl+C to stop.")
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start_time = time.time()
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while True:
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elapsed_time = time.time() - start_time
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current = keithley.current # Read current in Amps
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# Store data in lists
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t.append(elapsed_time)
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I.append(current)
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print("Time: " + str(elapsed_time) + "\t\t\t|\t\t\t Current: " + str(current) + " A")
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time.sleep(2)
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except KeyboardInterrupt:
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# Graceful Exit on Ctrl+C
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print("\nMeasurement stopped by User.")
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# --- FIX: Define data_df before using it ---
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data_df = pd.DataFrame({"Timestamp": t, "Current (A)": I})
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data_df.to_csv("demo_data.dat", index=False)
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print(f"Data saved to file: demo_data.dat")
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# Shutdown Sequence
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time.sleep(0.5)
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keithley.shutdown() # Ramps current to 0 and disables output
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print("Keithley closed.")
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# --- 2. CONNECT TO INSTRUMENT (V5 Logic) ---
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print(f"\nAttempting to connect to instrument at: {VISA_ADDRESS}")
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keithley = Keithley6517B(VISA_ADDRESS)
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print(f"Successfully connected to: {keithley.id}")
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# --- 3. CONFIGURE MEASUREMENT (V5 Logic) ---
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print("\nConfiguring instrument for measurement...")
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keithley.reset()
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# Set the function to resistance to ensure the ammeter is configured for zero correction.
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keithley.measure_resistance()
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# --- 4. PERFORM ZERO CHECK & CORRECTION (Exact V5 Logic) ---
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print("\nStarting zero correction procedure...")
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time.sleep(5)
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print("Step 1: Enabling Zero Check mode...")
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keithley.write(':SYSTem:ZCHeck ON')
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time.sleep(5)
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print("Step 2: Acquiring zero correction value...")
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#keithley.write(':SYSTem:ZCORrect:ACQuire')
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time.sleep(5)
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print("Step 3: Disabling Zero Check mode...")
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keithley.write(':SYSTem:ZCHeck OFF')
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time.sleep(5)
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print("Step 4: Enabling Zero Correction...")
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keithley.write(':SYSTem:ZCORrect ON')
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time.sleep(5)
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print("Zero Correction Complete.")
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# --- 5. SETUP AND PERFORM I-V SWEEP ---
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print(f"\nStarting I-V sweep from {start_v}V to {stop_v}V...")
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keithley.current_nplc = 1 # Set integration rate for noise reduction
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keithley.enable_source()
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with open(filename, 'w', newline='') as f:
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writer = csv.writer(f)
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writer.writerow([f"# Measurement Date: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}"])
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writer.writerow([f"# Sweep Parameters: Start={start_v}V, Stop={stop_v}V, Steps={steps}, Delay={delay}s"])
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writer.writerow(["Timestamp (s)", "Applied Voltage (V)", "Measured Current (A)", "Resistance (Ohm)"])
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start_time = time.time()
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for i, voltage in enumerate(voltage_sweep):
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keithley.source_voltage = voltage
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time.sleep(delay)
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resistance = keithley.resistance
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timestamp = time.time() - start_time
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#resistance = keithley.resistance
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current = voltage/resistance if resistance != 0 else float('inf')
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print(f"Step {i+1}/{steps}: V={voltage:.3f} V, I={current:.4e} A, R={resistance:.4e} Ω")
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data_point = [f"{timestamp:.3f}", f"{voltage:.4e}", f"{current:.4e}", f"{resistance:.4e}"]
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results.append(data_point)
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writer.writerow(data_point)
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print("\n--- I-V Sweep Complete ---")
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print(f"Data saved successfully to '{filename}'")
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except VisaIOError:
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print(f"\n[VISA Connection Error]")
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print(f"Could not connect to the instrument at '{VISA_ADDRESS}'.")
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print("Please check the address, cable connections, and if the instrument is on.")
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except ValueError:
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print("\n[Input Error] Please enter valid numbers for the sweep parameters.")
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except Exception as e:
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print(f"\n[An Unexpected Error Occurred] Details: {e}")
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finally:
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# --- 7. SAFELY SHUT DOWN (V5 Logic) ---
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if keithley:
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print("\nShutting down instrument...")
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keithley.shutdown()
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print("Voltage source OFF and instrument is safe.")
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# --- 8. PLOT RESULTS ---
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plot_results(results)
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print(f"Error with Keithley: {e}")

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