Agilent U12xxx series

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The Agilent U12xxx series are handheld digital multimeters, ranging from inexpensive all-purpose meters to industrial clamp meters.

Model Counts Supported
U1231A 6000 Yes
U1232A 6000 Yes
U1233A 6000 Yes
U1241A / U1241B 10000 Yes
U1242A / U1242B 10000 Yes
U1251A / U1251B 50000 Yes
U1252A / U1252B 50000 Yes
U1253A / U1253B 50000 Yes
U1271A 30000 No
U1272A 30000 No
U1273A 30000 No
U1273AX 30000 No

Is your model not supported yet? Get in touch! We need people to help us test other models in this series, and getting a new model supported is generally quick & easy.


All models communicate via an optically isolated serial connection, at 9600 bps, 8 bits, no parity, and 1 stop bit (9600/8n1). Connecting to the devices can be done either via USB (U1173A cable) or Bluetooth (U1177A interface).


All models in this series use generally the same protocol, with only minor differences between models -- and none within the same range.


Sending the command *IDN? causes the device to return a comma-separated four-field string, compatible with the identical GPIB command. The four fields are vendor name, model name, serial number and version:

Agilent Technologies,U1232A,MY52020136,V1.00


The FETC? command returns the current measured value, as a floating point ASCII string:


The value always takes exactly this form. If no valid measurement is available, i.e. the display shows "OL", the transmitted value is +9.90000000E+37.


The CONF? command queries the device's current measurement configuration.

U124xx and U125xx models

The output consists of the meter's mode, followed by a space, and then the meter's upper and lower ranges in that mode, separated by a comma. The mode may optionally include a colon followed by a code denoting a submode relevant to that major mode. For example, this is the AC voltage in the 1000mV range:

VOLT:AC +1.000000E+00,+1.000000E-04
Mode Meaning
VOLT Voltage, submode can be AC
CURR Current, submode can be AC
FREQ Frequency counter
DIOD Diode check
CONT Continuity
RES Resistance
CAP Capacitance
SCOU Switch counter
CPER Current loop, submode can be e.g. 0-20mA or 4-20mA.
T1 or T2 Temperature, submode can be K or J, denoting the thermocouple type. Instead of range, CEL or FAR is given, denoting the measurement is in Celcius or Fahrenheit.

U123xx models

This can be either one, two or three comma-separated fields. The number of fields depends on the first field's value, but the second field always denotes the measurement mode's range and resolution, and the third field is the current type (AC or DC).

Mode Resolution Current Meaning
V y y Volts
0 Range 600mV, resolution 0.1mV
1 Range 6V, resolution 1mV
2 Range 60V, resolution 0.01V
3 Range 600V, resolution 0.1V
MV y y Millivolts
1 Range 600mV, resolution 0.1mV
A y y Ampere
0 Range 6A, resolution 1mA
1 Range 10A, resolution 0.01A
UA y y Microampere
0 Range 60μA, resolution 0.01μA
1 Range 600μA, resolution 0.1μA
FREQ y y AC frequency
0 Always shows 0, even when the range is changed manually on the device. This is possibly a firmware bug.
RES y n Resistance
0 Range 600Ω, resolution 0.1Ω
1 Range 6kΩ, resolution 0.001kΩ
2 Range 60kΩ, resolution 0.01kΩ
3 Range 600kΩ, resolution 0.1kΩ
4 Range 6MΩ, resolution 0.001MΩ
5 Range 60MΩ, resolution 0.01MΩ
CAP y n Capacitance
0 Range 1000nF, resolution 1nF
1 Range 10μF, resolution 0.01μF
2 Range 100μF, resolution 0.1μF
3 Range 1000μF, resolution 1μF
4 Range 10mF, resolution 0.01mF
DIOD n n Diode


The STAT? command is used to query the current state of the device. The response is a quoted 21-byte string, like this:


U123xx models

Byte Value Meaning
1 Max/min/avg mode
0 Off
1 On
2 Relative measurement. The last value returned from FETC? before this mode was enabled denotes the stored reference value.
0 Off
1 On
3 Trig hold-log
0 Off
1 On
4 Auto hold-log
0 Off
1 On
5 LED flashlight
0 Off
1 On
6 LCD backlight
0 Off
1 On
7 Smoothing
0 Off
1 On
8 Temp/aux mode. When on and rotary switch is in position 5 (capacitance), CONF? returns MV,1,DC, but the value returned from FETC? instead denotes the temperature, in the unit (F or C) according to the meter's configuration.
0 Off
1 On
9 Unknown (always 0)
10 Beep frequency
0 4.2kHz
1 3.8kHz (default)
2 3.4kHz
3 3.2kHz
4 Off
11 Auto power-off (APO)
0 Off
1 On
12 Unknown (always 0)
13 Unknown (always L)
14 Unknown (always 0)
15 Unknown (always 0)
16 Rotary switch position
0 V/Zlow
1 Voltage AC
2 Voltage DC
3 Resistance
4 Diode
5 Capacitance
6 Current
7 Microcurrent
17 Continuity mode. When enabled, the value returned from FETC? is either NAN (no continuity) or any real value to denote continuity.
0 Off
1 On
18 Unknown (always 0)
19 Unknown (always 0, but briefly 1 at startup)
20 Unknown (always 0)
21 Unknown (always 0)