diff --git a/tools/README.md b/tools/README.md
index 138e864..d651096 100644
--- a/tools/README.md
+++ b/tools/README.md
@@ -33,8 +33,8 @@
 - Device (logs from Gonk) are set to: `--device-logfile gonk-device-log.txt`
 - CSV output is set to: `--csv-logfile gonk-csv-log.txt`
 
-**Note:** Log files are always appended to whenever running `gonk`. You can
-truncate the files on startup with `--truncate-logfiles`.
+**Note:** Log files are always erased on startup whenever running
+`gonk`. You can append instead with `--no-truncate-logfiles`.
 
 Logs are not normally written to the terminal but can be using `--log-to-stderr`.
 
@@ -44,7 +44,7 @@
 ### Start Logging ADC Measurements
 
 ```sh
-gonk --log-to-stderr --truncate-logfiles
+gonk --log-to-stderr
 ```
 
 This will provision the FPGA if necessary and begin logging ADC measurements.
diff --git a/tools/gonk_tools/adc.py b/tools/gonk_tools/adc.py
index dc771eb..d164ea6 100644
--- a/tools/gonk_tools/adc.py
+++ b/tools/gonk_tools/adc.py
@@ -13,6 +13,10 @@
 # the License.
 """ADC related math functions."""
 
+import logging
+
+_CSV_LOG = logging.getLogger('gonk.csv')
+
 # CHANNEL_MASK should be set to same value used by
 #   SelectContinuousReadAdcs in the MCU
 CHANNEL_MASK = 0b011100111001
@@ -62,6 +66,22 @@
     return retval
 
 
+def log_csv_header(channel_mask: int = CHANNEL_MASK) -> None:
+    csv_header = [
+        'host_time',
+        'delta_micros',
+    ]
+    for measurement_prefix in ['V', 'I', 'P']:
+        csv_header.extend(
+            [
+                f'{measurement_prefix}_{channel}'
+                for channel in get_channel_names(channel_mask)
+            ]
+        )
+    csv_header.append('comment')
+    _CSV_LOG.info(', '.join(csv_header))
+
+
 def get_resistances(channel_mask: int = CHANNEL_MASK) -> list[float]:
     """Returns list of shunt resistance values for the activated channels."""
     retval = []
diff --git a/tools/gonk_tools/gonk.py b/tools/gonk_tools/gonk.py
index 52df2c5..2a8d23e 100644
--- a/tools/gonk_tools/gonk.py
+++ b/tools/gonk_tools/gonk.py
@@ -36,6 +36,7 @@
     tokens,
 )
 
+from gonk_tools.adc import log_csv_header
 from gonk_tools.gonk_log_stream import GonkLogStream
 from gonk_tools.firmware_files import (
     BUNDLED_ELF,
@@ -165,7 +166,8 @@
     )
     parser.add_argument(
         '--truncate-logfiles',
-        action='store_true',
+        action=argparse.BooleanOptionalAction,
+        default=True,
         help=('Truncate logfiles on before logging.'),
     )
 
@@ -381,7 +383,7 @@
     merge_device_and_host_logs: bool = False,
     verbose: bool = False,
     log_to_stderr: bool = False,
-    truncate_logfiles: bool = False,
+    truncate_logfiles: bool = True,
 ) -> int:
     """Write a bitstream file over serial while monitoring output."""
 
@@ -470,6 +472,10 @@
         csv_filehandler.setFormatter(logging.Formatter(fmt='%(message)s'))
         _CSV_LOG.addHandler(csv_filehandler)
 
+        # Write the csv header if new file or truncate_logfiles is on.
+        if truncate_logfiles or not csv_logfile.is_file():
+            log_csv_header()
+
     if log_to_stderr:
         pw_cli_log.install(
             level=log_level,
diff --git a/tools/gonk_tools/gonk_log_stream.py b/tools/gonk_tools/gonk_log_stream.py
index 4726c06..7490f61 100644
--- a/tools/gonk_tools/gonk_log_stream.py
+++ b/tools/gonk_tools/gonk_log_stream.py
@@ -263,6 +263,8 @@
             ),
         )
 
+        # NOTE: If this format is changed the log_csv_header function
+        # must be updated in adc.py
         _CSV_LOG.info(
             '%s, %s, %s, %s, %s, %s',
             host_time,