diff --git a/conf.c b/conf.c
index 5904b91..9aa034c 100644
--- a/conf.c
+++ b/conf.c
@@ -97,6 +97,7 @@ static double combine_limit = 3.0;
 
 static int cmd_port = DEFAULT_CANDM_PORT;
 
+static int raw_measurements = 0;
 static int do_log_measurements = 0;
 static int do_log_statistics = 0;
 static int do_log_tracking = 0;
@@ -814,7 +815,10 @@ parse_log(char *line)
     log_name = line;
     line = CPS_SplitWord(line);
     if (*log_name) {
-      if (!strcmp(log_name, "measurements")) {
+      if (!strcmp(log_name, "rawmeasurements")) {
+        do_log_measurements = 1;
+        raw_measurements = 1;
+      } else if (!strcmp(log_name, "measurements")) {
         do_log_measurements = 1;
       } else if (!strcmp(log_name, "statistics")) {
         do_log_statistics = 1;
@@ -1468,8 +1472,9 @@ CNF_GetDumpDir(void)
 /* ================================================== */
 
 int
-CNF_GetLogMeasurements(void)
+CNF_GetLogMeasurements(int *raw)
 {
+  *raw = raw_measurements;
   return do_log_measurements;
 }
 
diff --git a/conf.h b/conf.h
index 22e6542..7ff1dba 100644
--- a/conf.h
+++ b/conf.h
@@ -52,7 +52,7 @@ extern char *CNF_GetDriftFile(void);
 extern char *CNF_GetLogDir(void);
 extern char *CNF_GetDumpDir(void);
 extern int CNF_GetLogBanner(void);
-extern int CNF_GetLogMeasurements(void);
+extern int CNF_GetLogMeasurements(int *raw);
 extern int CNF_GetLogStatistics(void);
 extern int CNF_GetLogTracking(void);
 extern int CNF_GetLogRtc(void);
diff --git a/doc/chrony.conf.adoc b/doc/chrony.conf.adoc
index 793e222..7a3bedb 100644
--- a/doc/chrony.conf.adoc
+++ b/doc/chrony.conf.adoc
@@ -1518,10 +1518,12 @@ The log files are written to the directory specified by the <<logdir,*logdir*>>
 directive. A banner is periodically written to the files to indicate the
 meanings of the columns.
 +
-*measurements*:::
+*rawmeasurements*:::
 This option logs the raw NTP measurements and related information to a file
-called _measurements.log_. An example line (which actually appears as a single
-line in the file) from the log file is shown below.
+called _measurements.log_. An entry is made for each packet received from the
+source. This can be useful when debugging a problem. An example line (which
+actually appears as a single line in the file) from the log file is shown
+below.
 +
 ----
 2016-11-09 05:40:50 203.0.113.15    N  2 111 111 1111  10 10 1.0 \
@@ -1563,6 +1565,12 @@ from the example line above):
 . Source of the local receive timestamp
   (_D_=daemon, _K_=kernel, _H_=hardware). [K]
 +
+*measurements*:::
+This option is identical to the *rawmeasurements* option, except it logs only
+valid measurements from synchronised sources, i.e. measurements which passed
+the RFC 5905 tests 1 through 7. This can be useful for producing graphs of the
+source's performance.
++
 *statistics*:::
 This option logs information about the regression processing to a file called
 _statistics.log_. An example line (which actually appears as a single line in
diff --git a/ntp_core.c b/ntp_core.c
index 014f999..cb38af6 100644
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -49,6 +49,7 @@
 /* ================================================== */
 
 static LOG_FileID logfileid;
+static int log_raw_measurements;
 
 /* ================================================== */
 /* Enumeration used for remembering the operating mode of one of the
@@ -353,7 +354,7 @@ NCR_Initialise(void)
   do_size_checks();
   do_time_checks();
 
-  logfileid = CNF_GetLogMeasurements() ? LOG_FileOpen("measurements",
+  logfileid = CNF_GetLogMeasurements(&log_raw_measurements) ? LOG_FileOpen("measurements",
       "   Date (UTC) Time     IP Address   L St 123 567 ABCD  LP RP Score    Offset  Peer del. Peer disp.  Root del. Root disp. Refid     MTxRx")
     : -1;
 
@@ -1687,7 +1688,7 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
   }
 
   /* Do measurement logging */
-  if (logfileid != -1) {
+  if (logfileid != -1 && (log_raw_measurements || synced_packet)) {
     LOG_FileWrite(logfileid, "%s %-15s %1c %2d %1d%1d%1d %1d%1d%1d %1d%1d%1d%d  %2d %2d %4.2f %10.3e %10.3e %10.3e %10.3e %10.3e %08"PRIX32" %1d%1c %1c %1c",
             UTI_TimeToLogForm(sample_time.tv_sec),
             UTI_IPToString(&inst->remote_addr.ip_addr),