diff --git a/prsctrl/prsctrl_interactive.py b/prsctrl/prsctrl_interactive.py
index 730ee97..5f08a34 100644
--- a/prsctrl/prsctrl_interactive.py
+++ b/prsctrl/prsctrl_interactive.py
@@ -43,6 +43,7 @@ from .measurement import measure_spectrum as _measure_spectrum, set_offsets_lase
 from .utility.prsdata import PrsData, plot_spectrum
 from .utility.config_file import ConfigFile
 from .utility.device_select import select_device_interactive, connect_device_from_config_or_interactive
+from .utility import duration_to_string
 from .update_funcs import Monitor
 
 import logging
@@ -170,6 +171,7 @@ def measure_spectrum(metadata:dict={},
     # measure/set offset
     full_scale_voltage = lockin_params["sensitivity_volt"]
     def set_offsets(name):
+        # TODO: use multithreading and queues
         shutter.close()
         plt_monitor.set_fig_title(f"Measuring baseline with lamp off")
         R_offset_fs, phase_offset_deg = set_offsets_laser_only(lockin, shutter, measurement_params["wait_time_s"])
@@ -236,23 +238,24 @@ def measure_spectrum(metadata:dict={},
 
 
 def sweep_ref():
-    wavelenghts = [500, 550, 650, 660, 670, 680]
-    frequencies = list(range(27, 500, 5))
-    frequencies = [111, 444]
+    wavelenghts = [500, 535, 565, 580, 700]
+    frequencies = list(range(27, 500, 2))
     lockin_params = {
         "time_constant_s": 10,
     }
     measurement_params = {
         "wavelengths_nm": wavelenghts,
     }
-    time_est = len(frequencies) * get_time_estimate(lockin_params=lockin_params, measurement_params=measurement_params, offset_with_laser_only=True, extra_wait_time_s=10)
-    print(f"Estimated time: {time_est}")
-    return
+    time_est = 1.15 * len(frequencies) * get_time_estimate(lockin_params=lockin_params, measurement_params=measurement_params, offset_with_laser_only=True, extra_wait_time_s=10)
+    print(f"Estimated time: {duration_to_string(time_est)}")
+    t_start = time.time()
     for f in frequencies:
-        dirname = f"2025-05-07_f-scan_f={f}_Hz"
-        lockin_params["frequency"] = f
+        dirname = f"2025-05-09_f-scan_f={f}_Hz"
+        lockin_params["frequency_Hz"] = f
         measure_spectrum(lockin_params=lockin_params, measurement_params=measurement_params, dirname=dirname, name="Frequency scan $f = {f}$ Hz")
         plt.close('all')
+    duration = time.time() - t_start
+    print(f"Measurement took {duration_to_string(duration)} (estimate was {duration_to_string(time_est)})")
 
 # DATA
 def data_load(dirname:str) -> tuple[np.ndarray, dict]:
diff --git a/prsctrl/tests/__pycache__/spectrum_sweeps.cpython-311.pyc b/prsctrl/tests/__pycache__/spectrum_sweeps.cpython-311.pyc
new file mode 100644
index 0000000..7cfa9a9
Binary files /dev/null and b/prsctrl/tests/__pycache__/spectrum_sweeps.cpython-311.pyc differ
diff --git a/prsctrl/tests/__pycache__/sweep_frequency.cpython-311.pyc b/prsctrl/tests/__pycache__/sweep_frequency.cpython-311.pyc
deleted file mode 100644
index 37d479b..0000000
Binary files a/prsctrl/tests/__pycache__/sweep_frequency.cpython-311.pyc and /dev/null differ
diff --git a/prsctrl/tests/spectrum_sweeps.py b/prsctrl/tests/spectrum_sweeps.py
new file mode 100644
index 0000000..033d6bc
--- /dev/null
+++ b/prsctrl/tests/spectrum_sweeps.py
@@ -0,0 +1,87 @@
+from prsctrl.utility.prsdata import PrsData
+import os
+import re
+import numpy as np
+import matplotlib.pyplot as plt
+
+def process_results(
+        data_dir,
+        dir_regex=r".*",
+        out_dir=None,
+        get_varied_param=lambda data: data.metadata["lock-in_settings"]["frequency_Hz"],
+        fig_suptitle="Frequency scan: <qty>",
+        xlabel="$f$ [Hz]",
+        what=["theta", "stheta", "dR_R", "sdR_R"],
+):
+    """
+    Process the results of several spectra recorded with one varying measurement or lock-in parameter.
+    
+    :param data_dir: Directory containing all data directories of the individual files
+    :param dir_regex: Regex for filtering data directories
+    :param out_dir: Directory into which the plots are saved
+    :param get_varied_param: lambda function getting the varied parameter value from a loaded PrsData object
+    :param fig_suptitle: Figure suptitle, <qty> will be replaced by the name of the quantity
+    :param xlabel: xlabel for the varied parameter
+    :param what: For which quantities to create plots
+    :return: 
+    """
+    data_dir = os.path.expanduser(data_dir)
+    if out_dir is None:
+        out_dir = data_dir
+    paths = os.listdir(data_dir)
+    data_dirs = []
+    for p in paths:
+        full_path = os.path.join(data_dir, p)
+        if not os.path.isdir(full_path): continue
+        m = re.fullmatch(dir_regex, p)
+        if m:
+            data_dirs.append(full_path)
+        else:
+            print(f"Unmatched directory {p}")
+    assert len(data_dirs) > 0
+    data_dirs.sort()
+
+    varied_params = []
+    data = {}
+    shape = None
+    wls = None
+    for d in data_dirs:
+        print(f"Getting data from {d}")
+        pd = PrsData(load_data_path=d)
+        # f = pd.metadata["lock-in_settings"]["frequency_Hz"]
+        varied_param = get_varied_param(pd)
+        # print(d, f)
+        sdata = pd.get_spectrum_data()
+        print(pd.wavelengths)
+        print(pd.data.keys())
+        if wls is None: wls = sdata[:,0]
+        if shape is None: shape = sdata.shape
+        else:
+            if shape != sdata.shape:
+                print(f"ERROR Shape mismatch for param={varied_param}: {shape} != {sdata.shape}")
+                continue
+                # raise ValueError(f"Shape mismatch for {d}: {shape} != {sdata.shape}")
+        varied_params.append(varied_param)
+        data[varied_param] = sdata
+    data_per_wl_and_vp = np.empty((shape[0], len(varied_params), shape[1]))
+    varied_params.sort()
+    for i in range(shape[0]):
+        for j, f in enumerate(varied_params):
+            data_per_wl_and_vp[i, j, :] = data[f][i,:]
+    print(f"Found wavelengths: {wls}")
+    n_cols = 2
+    n_rows = wls.shape[0] // n_cols + wls.shape[0] % n_cols
+    for qty in what:
+        fig, axs = plt.subplots(n_rows, n_cols, figsize=(8, 8))
+        axs = axs.flatten()
+        qty_idx = PrsData.default_spectrum_columns.index(qty)
+        fig.suptitle(fig_suptitle.replace("<qty>", PrsData.key_names[qty]))
+        for i, wl in enumerate(wls):
+            ax = axs[i]
+            ax.set_xlabel(xlabel)
+            ax.set_ylabel(PrsData.labels[qty])
+            ax.plot(varied_params, data_per_wl_and_vp[i, :, qty_idx])
+            ax.set_title(f"$\\lambda = {wl}$ nm")
+        fig.tight_layout()
+        fig.savefig(os.path.join(out_dir, f"result_{qty}.pdf"))
+    print(varied_params)
diff --git a/prsctrl/tests/sweep_frequency.py b/prsctrl/tests/sweep_frequency.py
deleted file mode 100644
index e655849..0000000
--- a/prsctrl/tests/sweep_frequency.py
+++ /dev/null
@@ -1,65 +0,0 @@
-from prsctrl.utility.prsdata import PrsData
-import os
-import re
-import numpy as np
-import matplotlib.pyplot as plt
-
-def process_results(data_dir, dir_regex=r"202.-..-.._f-scan_f=(\d+)_Hz", out_dir=None):
-    data_dir = os.path.expanduser(data_dir)
-    if out_dir is None:
-        out_dir = data_dir
-    paths = os.listdir(data_dir)
-    data_dirs = []
-    for p in paths:
-        full_path = os.path.join(data_dir, p)
-        if not os.path.isdir(full_path): continue
-        m = re.fullmatch(dir_regex, p)
-        if m:
-            data_dirs.append(full_path)
-        else:
-            print(f"Unmatched directory {p}")
-    assert len(data_dirs) > 0
-    data_dirs.sort()
-
-    frequencies = []
-    data = {}
-    shape = None
-    wls = None
-    for d in data_dirs:
-        print(f"Getting data from {d}")
-        pd = PrsData(load_data_path=d)
-        f = pd.metadata["lock-in_settings"]["frequency_Hz"]
-        # print(d, f)
-        sdata = pd.get_spectrum_data()
-        print(pd.wavelengths)
-        print(pd.data.keys())
-        if wls is None: wls = sdata[:,0]
-        if shape is None: shape = sdata.shape
-        else:
-            if shape != sdata.shape:
-                print(f"ERROR Shape mismatch for f={f}: {shape} != {sdata.shape}")
-                continue
-                # raise ValueError(f"Shape mismatch for {d}: {shape} != {sdata.shape}")
-        frequencies.append(f)
-        data[f] = sdata
-    data_per_wl_and_f = np.empty((shape[0], len(frequencies), shape[1]))
-    frequencies.sort()
-    for i in range(shape[0]):
-        for j, f in enumerate(frequencies):
-            data_per_wl_and_f[i, j, :] = data[f][i,:]
-    print(f"Found wavelengths: {wls}")
-    n_cols = 2
-    for qty in ["theta", "stheta", "dR_R", "sdR_R"]:
-        fig, axs = plt.subplots(wls.shape[0]//n_cols, n_cols, sharex=True, figsize=(8, 8))
-        axs = axs.flatten()
-        qty_idx = PrsData.default_spectrum_columns.index(qty)
-        fig.suptitle(f"Frequency scan: {PrsData.key_names[qty]}")
-        axs[-1].set_xlabel("Modulation Frequency $f$ [Hz]")
-        for i, wl in enumerate(wls):
-            ax = axs[i]
-            ax.set_ylabel(PrsData.labels[qty])
-            ax.plot(frequencies, data_per_wl_and_f[i, :, qty_idx])
-            ax.set_title(f"$\\lambda = {wl}$ nm")
-        fig.tight_layout()
-        fig.savefig(out_dir + f"result_{qty}.pdf")
-    print(frequencies)
diff --git a/prsctrl/utility/__init__.py b/prsctrl/utility/__init__.py
index e69de29..58e2faa 100644
--- a/prsctrl/utility/__init__.py
+++ b/prsctrl/utility/__init__.py
@@ -0,0 +1,25 @@
+timedelta = [("d", 24*3600), ("h", 3600), ("m", 60), ("s", 1)]
+def duration_to_string(duration: float) -> str:
+    """
+    Convert a duration in seconds to a string of the form "<days>d <hours>h <minutes>m <seconds>s"
+    where only the largest units are included.
+    Parameters
+    ----------
+    duration: float
+        Duration in seconds.
+
+    Returns
+    -------
+       String representation of the duration.
+    """
+    include = False
+    s = ""
+    sign = 1 if duration > 0 else -1
+    time_left = abs(int(duration))
+    for i, (unit, unit_seconds) in enumerate(timedelta):
+        t = int(time_left / unit_seconds)
+        if t != 0 or include or unit == "s":
+            s += f"{sign*t:02}{unit} "
+            include = True
+        time_left %= unit_seconds
+    return s.strip()
diff --git a/prsctrl/utility/__pycache__/__init__.cpython-311.pyc b/prsctrl/utility/__pycache__/__init__.cpython-311.pyc
index 23ea318..658c008 100644
Binary files a/prsctrl/utility/__pycache__/__init__.cpython-311.pyc and b/prsctrl/utility/__pycache__/__init__.cpython-311.pyc differ
diff --git a/prsctrl/utility/__pycache__/prsdata.cpython-311.pyc b/prsctrl/utility/__pycache__/prsdata.cpython-311.pyc
index ba03300..ee2282b 100644
Binary files a/prsctrl/utility/__pycache__/prsdata.cpython-311.pyc and b/prsctrl/utility/__pycache__/prsdata.cpython-311.pyc differ
diff --git a/prsctrl/utility/prsdata.py b/prsctrl/utility/prsdata.py
index 4ac0d50..9aa2e6b 100644
--- a/prsctrl/utility/prsdata.py
+++ b/prsctrl/utility/prsdata.py
@@ -162,8 +162,11 @@ class PrsData:
         "dR": r"$\Delta R$ [V]",
         "R": r"$R$ [V]",
         "theta": r"$\theta$ [°]",
+        "sdR_R": r"$\sigma_{\Delta R/R}$",
+        "sdR": r"$\sigma_{\Delta R}$ [V]",
+        "sR": r"$\sigma_R$ [V]",
+        "stheta": r"$\sigma_\theta$ [°]",
     }
-    labels |= {f"s{k}": f"$\sigma_{{{v[1:]}}}" for k, v in labels.items()}
     def get_spectrum_data(self, wavelengths=None, keys=None) -> np.ndarray:
         """
         Return the spectral data for the specified keys and wavelengths.