using software from: https://github.com/WhiteyCookie/Bitaxe-Core-Voltage-Benchmark

Nerdaxe with individual 5 volt power supply:

$ python3 /usr/local/bin/bitaxe_corevoltage_benchmark.py
Enter the IP address of the Bitaxe (e.g., 192.168.2.117): 192.168.42.79
Enter the duration for data collection (in minutes): 10
Enter the interval between data samples (in seconds): 2
Starting data collection every 2 seconds for 10 minutes.
300 samples to be collected.
270 samples left to collect. Time elapsed: 1 min and 1 sec.
240 samples left to collect. Time elapsed: 2 min and 4 sec.
210 samples left to collect. Time elapsed: 3 min and 8 sec.
180 samples left to collect. Time elapsed: 4 min and 11 sec.
150 samples left to collect. Time elapsed: 5 min and 13 sec.
120 samples left to collect. Time elapsed: 6 min and 16 sec.
90 samples left to collect. Time elapsed: 7 min and 18 sec.
60 samples left to collect. Time elapsed: 8 min and 20 sec.
30 samples left to collect. Time elapsed: 9 min and 22 sec.
Summary of voltage differences:
Core Voltage Actual was on average 0.63% below Core Voltage (1192.474 V), which corresponds to approximately 1.90 minutes of the total monitoring period. On average, Core Voltage Actual was 1.58% higher than Core Voltage (1218.922 V), which corresponds to approximately 7.70 minutes of the total monitoring period.
Lowest Core Voltage Actual Spike: 1183.000 V
Highest Core Voltage Actual Spike: 1259.000 V
Detailed summary (JSON format):
{
    "Average Percentage below": -0.6271929824561403,
    "Average_Percentage above": 1.576839826839827,
    "Average Duration below": 1.9,
    "Average Duration above": 7.7,
    "ASIC Voltage Requested": 1200.0,
    "Average Voltage below": 1192.4736842105262,
    "Average Voltage above": 1218.922077922078,
    "Lowest Voltage measured": 1183,
    "Highest Voltage measured": 1259
}

-------------------

HEX unit with (shared) industrial power supply 12 volt:
HEX has onboard 12 -> 5 volt DC chopper

$ python3 /usr/local/bin/bitaxe_corevoltage_benchmark.py
Enter the IP address of the Bitaxe (e.g., 192.168.2.117): 192.168.42.82
Enter the duration for data collection (in minutes): 10
Enter the interval between data samples (in seconds): 2
Starting data collection every 2 seconds for 10 minutes.
300 samples to be collected.
270 samples left to collect. Time elapsed: 1 min and 0 sec.
240 samples left to collect. Time elapsed: 2 min and 2 sec.
210 samples left to collect. Time elapsed: 3 min and 4 sec.
180 samples left to collect. Time elapsed: 4 min and 6 sec.
150 samples left to collect. Time elapsed: 5 min and 8 sec.
120 samples left to collect. Time elapsed: 6 min and 10 sec.
90 samples left to collect. Time elapsed: 7 min and 11 sec.
60 samples left to collect. Time elapsed: 8 min and 13 sec.
30 samples left to collect. Time elapsed: 9 min and 15 sec.
Summary of voltage differences:
Core Voltage Actual was on average 0.49% below Core Voltage (1144.416 V), which corresponds to approximately 9.70 minutes of the total monitoring period. On average, Core Voltage Actual was 0.00% higher than Core Voltage (1150.000 V), which corresponds to approximately 0.00 minutes of the total monitoring period.
Lowest Core Voltage Actual Spike: 1143.000 V
Highest Core Voltage Actual Spike: 1145.000 V
Detailed summary (JSON format):
{
    "Average Percentage below": -0.48558195129239506,
    "Average_Percentage above": 0,
    "Average Duration below": 9.7,
    "Average Duration above": 0.0,
    "ASIC Voltage Requested": 1150.0,
    "Average Voltage below": 1144.4158075601374,
    "Average Voltage above": 1150.0,
    "Lowest Voltage measured": 1143,
    "Highest Voltage measured": 1145
}